In November 1984, the tenth Fighting Fantasy gamebook, Steve Jackson's House of Hell, was unleashed upon the world, and marked many significant divergences from the established format. Until now, the series had been very much swords-and-sorcery, with a single excursion into science-fiction for the fourth book, Starship Traveller, also by Jackson; House of Hell was the first book to feature a contemporary setting, and the only one released in the original series' lifetime (it would take until 2012 for the 21st century relaunch to give us a second, Ian Livingstone's Blood of the Zombies), as the player character's car breaks down and leaves them with no choice but to seek refuge in the House of Drumer, which contains just about every horror movie encounter known to man, brought to life by Tim Sell's impressively macabre illustrations. It's also an exceptionally difficult puzzle-box of a book, requiring a strict sequence of moves to be done in an exact order, and featuring many tricks and traps including extended dead-ends where all the paths ultimately lead to death and secret sections not directly accessible from other ones.
In the same month as the book was released, though, a preview version (known as The House of Hell, with the definitive article) was published in the third issue of the official Fighting Fantasy magazine, Warlock. That version runs to 185 sections (compared to the full-length version's 400), but it isn't simply the book chopped in half -- it's a truncated version, with many of the rooms shuffled around and bits missing, but it is a complete adventure in its own right which keeps recognisably the same basic story. As the editorial in that issue puts it: "Steve's House of Hell is the one in this issue of Warlock, but turned inside out. The rooms have been jumbled, there are some cunning secret passages to find and the important clues are in totally different places. Getting through the mini-adventure will not help you at all!"
So what exactly is different?