Jules Verne's 20,000 Leagues Under the Sea, set in Victorian times and featuring a technologically advanced submarine, would qualify if not for the minor detail that the book was written during the Victorian era, thus making it the main inspiration for the movement rather than a part of it.
Rick Riordan's tribute/sequel, Daughter of the Deep, featuring the same submarine, definitely qualifies, having been written in 2021.
The Bas-Lag Cycle is particularly punky steampunk mixed with fantastic elements and New Weird worldbuilding. The books contain normal steampunk trappings like trains and zeppelins, up into fantastical creations like Powered Armor and steam-powered prosthetic organs.
Blood of Earth is set in an alternate Steampunk 1900s San Francisco.
Lavie Tidhar's Bookman series combines real historical characters like Harry Houdini, original ones and fictional like Lucy Westenra and Mycroft Holmes. Oh, and David Icke would be right in this universe — the British royal family really are alien reptiles, only it's not a conspiracy, everyone knows about it and most people are quite content. The French royals were too, but they got overthrown by an alliance of humans and automatons.
A slight example in Borderlands, where the once-powerful world of Centrum has been reduced to this after a petroleum-consuming plague has been unleashed on the world, destroying all oil-based products (including plastics) in a matter of hours. Electricity is practically non-existent, as plastics allow for cheap insulation of wires. Without them, other types of insulation are simply not cost-effective. Old steam trains are brought back into service, and the railroaders become the most powerful NGO in Centrum, as all supplies and trade are dependent on them. Modern-day guns still work, though (at least, those that don't have any plastic parts).
The Burton & Swinburne Series is set in an alternative history version of the world which ended up becoming much more advanced due to a time traveler going back in time and accidentally gets queen Victoria killed as well as accidentally telling someone about various technology from the future which ends up creating an alternative reality in which hybrid animals, highly advanced robots, and psychic powers exist.
"C-Chute" is an early example, taking place on a steam-powered spaceship.
Jay Lake's Clockwork Earth series is set In a World… where the "Watchmaker analogy" of Deism is real in the most literal sense: the world is divided at the equator by an insurmountable wall that connects the Earth to the heavens with giant brass cogs. Instead of stars, you can see other planets' clockwork tracks. The Britain Empire retains all her Northern Hemisphere lands, including the Americas, the Victorian/Edwardian era protagonists have all sorts of interesting steampunk devices, including airships, and the Angel Gabriel is made of brass and cogs.
Dawn of Steam shows us a world that is beginning to evolve from one like our own just after the Napoleonic War into a fully fledged steam punk setting. That being said the series still prominently depicts a Cool Airship and steam-fueled Power Armor.
The Neo-Victorian clade from The Diamond Age deliberately modelled their technology to be aesthetically Victorian and steampunk-ish despite having a full mastery of nanotechnology.
William Gibson and Bruce Sterling's 1990 Alternate History novel The Difference Engine, while not actually the first instance of Steam Punk, is credited with popularizing the genre in the west. It's also a lot more "punky" than the ones that followed, with its steam-driven Dickensia practically qualifying as a Dystopia. It was intentionally written as a Cyberpunk novel, set in a Victorian setting.
Doctor Grordbort's Contrapulatronic Dingus Directory is a stimulating compendium of Cool, but Inefficient destructive devices, electro-motive engines and health-enhancement machines for all enthusiasts of the genre known as "steam-punk," plus those gentlemen of leisure who feel that their masculinity would be grossly enhanced by the acquisition of an Exterminator of Prodigious Dimensions.
In the Past Doctor Adventures novel Imperial Moon, steampunk technology is technically a key part of the plot, as the Fifth Doctor and Turlough learn of the existence of the British Imperial Spacefleet in 1878. While Turlough doubts the concept, the Doctor notes that technically Victorian Britain could have built a structurally sound spaceship but would have just been unable to get it airborne, with the engines depicted in the novel devised through indirect alien interference.
In the Doctor Who Missing Adventures novel The Crystal Bucephalus, the control room for the eponymous time displacement restaurant is all brass keyboards and chunky bronze levers. Since this is very out of place with the rest of 10th millennium technology (but not with the ambience of the Bucephalus itself), the Doctor correctly identifies it as a purely aesthetic affectation on the part of the engineer, similar to the TARDIS secondary control room.
Draconis Memoria: The setting of the series is roughly analogous to late nineteenth century Europe, with pre-modern firearms, steamship equivalents, massive corporations and large-scale colonization of unexplored continents. The differences lay primarily in the power source much of the worlds technology employs (blood-blessed powers) and, of course, with the creatures native to the exotic continent being dragons and primeval reptiles rather than elephants and lions.
The Edge Chronicles occasionally dip into this aesthetic. And if they weren't steampunk before, they certainly are as of The Immortals. (Which makes sense, given that in that book the Edge is going through its equivalent of the Industrial Revolution.)
The Exile's Violin, by R. S. Hunter, the beginning of a planned "Tethys Chronicles" series.
S.S. Taylor's The Expeditioners takes place in an alternate present where computers were invented in the Gilded Age and crashed on a massive scale sometime in the early '80s leaving society to go back to older technologies.
The Falling Machine by Andrew P. Mayer (Book 1 of an ongoing trilogy) is about a Steampunk Superhero team called The Society of Paragons.
Theodore Judson's Fitzpatrick's War, a Roman à Clef of the life of Alexander the Great, takes place in a steampunk future environment. It's later revealed that this is because a secret society set up a Star Wars Defense Grid in space to fry any electronic devices on the planet's surface with giant lasers.
Older Than Radio: Anthony Trollope wrote mainly fairly realistic novels. But towards the end of his life, in the early 1880s, he wrote The Fixed Period which imagined a world of his future in which people got around on "steam-powered tricycles" and played cricket with "a mechanical steam bowler."
Dime Novel hero Frank Reade, like Wells and Verne, can be counted as another example of steam punk avant la lettre; the Reade stories are full of steam powered inventions of all kinds. Perhaps the most famous was The Steam Man of the Plains, a kind of proto-robot that could shoot fiery missiles. For that matter, Frank Reade can also be counted as actual steampunk, courtesy of Paul Guinan and Anina Bennett's FRANK READE: Adventures in the Age of Invention, a fictionalized biography of the Victorian inventor.
Havemercy features a military fleet of magical clockwork dragons. This may technically fall under "clockpunk" more, but it is often associated with the Steampunk aesthetic.
Hermeticon by Vadim Panov is a space age steampunk where people travel space with alchemy-powered zeppelins.
The His Dark Materials series includes steampunk elements, especially for Lyra's world. The trope is minimally deployed—and Pullman never goes out of his way to describe any obviously Steampunk technology or settings. For example, the power source of choice is electricity (referred to as anbaric power—from amber, which the Greeks call electrum) supplied by nuclear generators (atomcraft works—from the German Atomkraftwerk), and science is mostly working on particle physics. The book feels more steampunk than it is probably because the opening chapters take place in the rather old-fashioned University of Oxford, features a few incidental airships, and prominently features a cast of powerful politicians, aristocrats, industrialists, and explorers with high-flown titles who bestrode the world with a swagger and a Mighty Whitey self-confidence that can only be described as Victorian. Not to mention the almost Dickensian take on English class relations.
The film, on the other hand, plays the steampunk for all the trope's worth.
The TV series, however, averts this, featuring an overall more modern-looking aesthetic to Lyra's world.
K. W. Jeter's Infernal Devices (not to be confused with the Cassandra Clare novel), arguably the book that started it all. Contains mad scientists, space travel, time travel, clockwork robots, and fish-men!
Cassandra Clare's The Infernal Devices series is a Gaslamp Fantasy mixed with Steampunk elements. Set a century before her The Mortal Instruments universe, the books follow a young woman named Tessa as she attempts to deal with numerous magical plots against her as well as her friends. Technology is supplemented by magic in the books, making the trope of Steampunk justified.
The Jackelian Series is set in an Alternate History — very alternate — with airships, submersables, pneumatic buildings, steam-powered intelligent robots, flintlock pistols, gas masks, goggles, bionic characters...and mutants, fey creatures, aliens and practically everything else you could imagine. It starts with The Court of the Air, with follow-ups including The Kingdom Beyond the Waves, Rise of the Iron Moon, Secrets of the Fire Sea, Jack Cloudie and finally From the Deep of the Dark. Each novel is standalone with a few continuing characters.
The Land of Oz books, surprisingly enough. Yes, the place is loaded with magic, but it also has some interesting technological features like prosthetics (Nick Chopper, Captain Fyter), cell phones (The Wizard, on one of his return trips, whips one up), Ridiculously Human Robots (Tik-Tok), artificial life forms (ChopFyt), and cities that can sink or rise mechanically (plot point in Glinda of Oz).
Leviathan is about an Alternate History version of World War I fought between the 'Darwinists' (the Entente Powers), who use fabricated animals, and the 'Clankers' (Central Powers), who use mechanical walkers and zeppelins.
In The Lost Thing, both the creature and the verse itself are rather steampunky in appearance.
The Lotus War has a steampunk version of Japan. It's a heavy deconstruction, since they've completely ruined the environment.
The Ministry of Peculiar Occurences series by Pip Ballantine features adventures of two secret agents of a unique government agency that specializes in odd cases in a steampunk Victorian England.
Balogun Ojetade's Moses: The Chronicles of Harriet Tubman, an early work of what the author dubbed "steam funk" (black steam punk), has real life abolitionist Harriet Tubman fighting the forces of evil with superpowers in a steam punk alternative version of the US shortly after the assassination of Abraham Lincoln.
The Parasol Protectorate Series by Gail Carriger features heavy Steampunk elements, along with an alternate history London where supernaturals influence society.
The Pax BritanniaShared Universe, including Jonathan Green's series about Ulysses Quicksilver, Agent of the Empire, and Al Ewing's Mexican adventurer El Sombra (overlaps with Cattle Punk). Contains lots of Shout Outs.
Downplayed The Peshawar Lancers by S. M. Stirling. In the Victorian era, meteor strikes devastated the Northern hemisphere, which obviously derailed scientific progress, so things like the internal combustion engine were not invented, and generations of engineers have focussed on refining and improving the technology they already have rather than making anything new. By 2025, technology is roughly at the same level as it was in the late 1800's, albeit more efficient. There are a few differences: electric lights have been invented, but they're still rare and expensive and steam powered cars are a relatively recent invention. They do have the standard zeppelins and difference engine however.
In Ian McDonald's PlanesrunnerEarth 3 or E3 is a mix of this and Raygun gothid. Coal is the main fuel because there's no oil but there are no steam engines because the electric motor was invented first. There are airships but their gasbags are woven of carbon nanotubes, vehicles all operate off a power grid but their computers or "comptaters" use vacuum tubes. The protagonist refers to it as "electropunk".
In Please Don't Tell My Parents I'm a Supervillain, Penny's first invention, the Machine, is actually a wind-up device that consumes energy from any and all nearby sources rather than something more electronic. It's even mentioned to be filled with incredibly fine gears. Most of the rest of the things she makes aren't steam punk, though.
Queen Victoria's Bomb by Ronald W. Clark, about the invention of an atomic bomb a hundred years earlier. It has limited consequence however, as knowledge of the invention is suppressed by the Queen.
Several of Robert Rankin's novels are set in/relate to a high-tech Victorian age whose history was supressed by those fiendish witches The Chiswick Townswomen's Guild.
Spanish book La República Pneumática takes place in a Roman Republic restablished by Emperor Claudius, thanks to the steam (or pneuma) technology developed by Hero of Alexandria. The steam certainly changed things — trains and zeppelins are common, and coal-powered automatons are toys — but did nothing for many other issues — corruption is high as hell, and slavery is still rampant. The story takes place in the days leading to the 1000th anniversary of Rome's foundation, the protagonist being a young teenager that gets accidentally involved in a conspiracy to murder the Consul.
The Reconstruction Series is an American Western steampunk. The main method of power is electricity, making it specifically Teslapunk.
One of the parallel worlds in Rough Draft is an example of this trope. Earth 3 (AKA Veroz) lacks petroleum, thus preventing the jump to internal combustion and the development of any petroleum-based products (including plastics). At one point, the protagonist witnesses a steam tank defending a coastal city-state (nation-states do not exist in this world) from a kraken.
Safehold: Since they are unable to use electrical devices (including spark plugs) for fear of setting off the Rakurai satellites, Safehold ends up using steam power for a lot of things that used electricity or internal combustion engines in Real Life.
The Saga of Recluce flirts with the genre. It never quite gets there, however; the leadership of the titular nation deliberately withholds the steam-based technology from general knowledge in an effort to preserve the status quo, but that doesn't stop things from getting out of hand in The Death of Chaos.
Senlin Ascends is about a man who gets separated from his wife on their honeymoon in the eponymous Tower of Babel, and atarts looking for her throughout its myriad ringdoms. On the way he makes a lot of enemies and a scant few friends, becoming an airship captain in the process.
Andrew Mayers Society of Steam series which is about steam powered superheroes and villains in the Gilded Age.
The Supervillainy Saga's Tales of Supervillainy: Cindy's Seven, The World Emperor was a steampunk version of Doctor Doom who created his own country off an isolated Scottish Island. It's now a theme park that sells tacky genre merchandise with free googles.
Steampunk meets Robot Uprising in the short story Trois morceaux en forme de mechanika by Gord Sellar, in which an uprising of mechanikae beginning in 1897 Bohemia leads to the destruction of humanity and their culture, with a melancholy aftermath as the robots try to come to terms with what they've done through art and music.
William Pene Du Bois' The Twenty One Balloons has a lot of steampunk sensibilities in its descriptions of wonderful, but useless late-1800s steam-powered gadgetry, including a bed with infinite sheets and an electrified room where the furniture can be driven via bumper-car technology. There's also a dash of Cool Airship in its many balloon devices.
The Vampire Empire trilogy by Clay and Susan Griffith
Michael Moorcock's The Warlord of the Air was an early example of this trope.
S. M. Peters's Whitechapel Gods has a Steampunk god, in addition to a clockwork counterpart, both of them with their own armies of coal-driven and clockwork soldiers, respectively. This particular novel draws heavily on the "punk" park of Steampunk; it's not a happy place.
The Wraith Knight series by C.T. Phipps is an unusual example as it takes place in a High Fantasy setting but which has combined technology with magic after the last war between the Dark Lord and The Alliance. While the protagonist is effectively a Ringwraith, he has to deal with an enormous clockwork spider and the flying navy of the Empress.
. The Ghost (2010) is set in the same universe but forty years later, when the world is transitioning to Diesel Punk.