Ascended Fanon: The series initially didn't have an official title, but was referred to by everyone as "the Alex Rider books". The 2010 rebranding has officially adopted "Alex Rider" as the series title.
Breakthrough Hit: Although Anthony Horowitz had been writing for children since 1979, and had been a fairly prolific television writer since the mid-eighties, Alex Rider is unquestionably his best-selling series. This is lampshaded and parodied in Daniel Hawthorne Novels, where Horowitz himself plays The Watson and people are constantly asking him about the Alex Rider books.
Contest Winner Cameo: Ark Angel and Scorpia Rising both featured gadgets designed by competition winners (the sleeping-gas-exhaling/exploding inhaler and the Hat Nav, which never actually got used).
The "cement shoes" method of execution (weighing down the victim with concrete and throwing them into a river) is described as a common practice by mafia gangs in Never Say Die, when the method is largely fictional and only one real life case has ever been authenticated.
Creator Backlash: Anthony Horowitz has stated that he dislikes Jack Starbright's name, and would have given her a different one if he had the opportunity.
Executive Meddling: Anthony Horowitz's publisher tried quite hard to get the title of Crocodile Tears changed, as they believed the saying it refers to was too obscure and most readers would not understand what the title meant. Horowitz pushed back, and eventually they relented on condition that the book included a definition of the term as a epigraph.
Sequel Gap: The first six books averaged out as an annual event, and were followed by a two-and-a-half year gap before the release of Snakehead. Crocodile Tears was released just over two years later, and Scorpia Rising followed slightly under 18 months later. The revived series will see the longest gap between books yet, with three years between Never Say Die and Nightshade (not including the time between Scorpia Rising and NSD where the series was officially over), although this was broken up with the short story collection Secret Weapon coming out inbetween them.
Teasing Creator: Anthony Horowitz has indulged in this on occasion; he teased two plot points from Scorpia Rising, namely that one of the villains in a previous book didn't really die and that Smithers had a big secret, before Crocodile Tears was even written.
Combined with Comic-Book Time, with the world incorporating new technology and referencing events that occurred throughout real history.....all without the author bothering to advance the story universe more than a year. The eponymous Stormbreaker computer isn't that impressive by modern standards and is rather quickly eclipsed by the iPhones that somehow appear just a year later.
At the beginning of the series, Alex is provided with a Gameboy by Smithers full of secret gadgets, and at the end of Crocodile Tears he's talking to Jack about Assassin's Creed.
There were plans for a series of film adaptations, with potential that it'd become the next Harry Potter. All that went out the window entirely after the film adaptation of Stormbreaker flopped commercially and at best received lukewarm reception, plus Horowitz admitting that the series doesn't translate well to the big screen.
Horowitz originally intended to write the Yassen Gregorovich prequel, which eventually became Russian Roulette, after Ark Angel; it would have been called Yassen. However, when he mentioned the idea during several visits to schools, it got a lukewarm reception and he decided to shelve the idea until he was completely finished with Alex.
The original plot of the book which eventually became Scorpia Rising was, in its early stages, very different: Alex would have gone to Cairo as part of a school exchange program, unaware that it had been arranged by Alan Blunt behind his back, and rather than being a Red Herring as it is in the final book, the school would have been pivotal to a completely different climax when it was taken over by terrorists.
At the time when Scorpia Rising was still intended to be the final book in the series, Horowitz floated the idea of writing a follow-up book featuring Alex as an adult several years down the line, which would have been aimed at an older audience. His decision to revive the series with Never Say Die, set only a few weeks afterwards, has likely put paid to that (although his publishers disliked the idea anyway).
Although it is implied in the text, Horowitz confirmed that the assassin who shoots Alex in the final chapter of Scorpia was later killed by Scorpia when they learned Alex was still alive.
Sayle Enterprises was closed down after the events of Stormbreaker, and parts of the business are sold, with what remains eventually becoming a "respectable concern".
Eagle Strike was variously known in its early stages as Eagle Eye, Gameslayer and Never Play Dead (the last of which appears to be an Orphaned Reference).
The original title for Crocodile Tears was Endurance Point, which received a negative response when Horowitz mentioned it to schoolchildren.
General Trivia
Herod Sayle, the Big Bad of Stormbreaker who plans to kill every schoolchild in Britain, is often incorrectly assumed to be named after the Biblical character. In truth, his name is meant to be a pun on "Harrods sale" (in reference to the London department store).
The original draft of Stormbreaker did not have any gadgets in it, because Horowitz felt they were unrealistic and disliked their usage in the recent James Bond films at the time. They were only added after Horowitz's editor and several children he met at public events were disappointed at their absence.
Point Blanc was going to be the first book, but Horowitz worried that the cloning idea was too fantastical to open the series with, so Stormbreaker got written instead.
The infamous Downer Ending of Scorpia, when Alex gets shot by a sniper, was a last-minute addition when Horowitz realised it would not make sense if Scorpia did not try to take their revenge on Alex. (The penultimate chapter contains a remnant of the fact that it would originally have been the last chapter; Mrs Jones tells Alex they'll get someone to drive him home, only for Alex to then leave on foot without explanation.)
Abdul-Aziz Al-Razim, the Big Bad of Scorpia Rising, was originally called Kalid Aziz Al-Kazim. The change appears to have been made quite late in the day, as a blog post on Horowitz's website written when Horowitz only had two chapters of the book left to write still uses the original name.
Alex is named after a Bond girl - he gets his surname from Honeychile Rider from Dr. No. Other names Horowitz considered were Jack Banning, Tom Summers, Zac Marshall, Scott Winters, Dylan Beckett, Miles Longman, Sean Reeves, Jake Keaton, Adam Whitehead, Kai Bexter, Marcus Edwards, Liam Skye, Connor West, Kyle Fisher, Bradley Roberts, Callum Gates, Rupert Halliwell and Ben Shires.
as "The Cribber" in Skeleton Key.