Audience-Alienating Ending: In a cross with Angst Aversion, it's hard to seek this book knowing it has a massive Downer Ending - both the radio version and Eoin Cofler's sequel undid it by saving some characters (Douglas Adams wanted to do it too, but died before being able to write the book).
He's Just Hiding: Douglas Adams said in The Salmon of Doubt that he wanted to write a sixth book to undo the fifth's depressing ending, leading fans to assume the characters all somehow survived.
Remember when Arthur first encountered the Vogons, and wished he had a daughter so he could tell her never to marry one? In this book, he ends up with Random. Be Careful What You Wish For, Mr. Dent. (He does, in fact, forbid her from marrying a Vogon, much to her bewilderment.)
Arthur Dent becomes the village's esteemed Sandwich Maker. The Subway restaurant chain dubbed their sandwich makers "sandwich artists".
The year after the book came out, a new edition of The Hitch-Hiker's Guide to Europe was released. Rather than the original cheap paperback, this was in the same big, glossy format as other travel books by the same publisher. If it weren't for the fact the dates don't work, it would be hard to avoid assumuing that Vann Harl's description of the Guide Mk 2 as "we don't sell to penniless hitch hikers. What a stupid notion that was! Find the one section of the market that, more or less by definition, doesn't have any money, and try and sell to it. No. We sell to the affluent business traveller and his vacationing wife" was a deliberate swipe at this.
Inferred Holocaust: The destruction of "every Earth in every reality" and all their inhabitants sounds bad enough, but it's left to the reader to realize that that includes NowWhat, the King, and probably even the dolphins. (NowWhat may be a Crapsack World, but it puts a human face on those alternate Earths and shows just how diverse they were.)
