The Crown of Kings is the fourth and final book of Steve Jackson's Sorcery!, Jackson's four-volume epic, arguably the pinnacle of the solo gamebook format, and Jackson really goes to town on making it as difficult as possible. One of the author's favourite tricks for cheat-proofing his books is reference modifiers -- at certain sections, there will be a nonstandard action you can take if you have a certain item or piece of knowledge by modifying the number of the section you are on to discover a secret, otherwise unknowable section. Players not in possession of this will not have a clue the option is even there.
Jackson had been developing this idea across his Fighting Fantasy books House of Hell and Appointment with F.E.A.R., as well as the second and third Sorcery! books, but The Crown of Kings is where he really perfects the idea, and the book is stuffed with them. But there are three I want to highlight in particular.
There is a special bonus if you killed all of the titular tuataras in the preceding book, The Seven Serpents. As the Serpents were bringing the Archmage of Mampang a message warning him about you, laying waste to all of them means no word of your mission has reached the Fortress and you have the element of surprise on your side.
This is deployed with the following mechanic: if you ever reach a reference where a character refers to you as 'the Analander', you should deduct 40 from the number of that section and turn to the new number for an alternate version of the encounter where you are not recognised. This is largely very cleverly realised; I particularly enjoy one scenario where you accidentally give the game away by telling someone where you come from and have to stop using the modifier. (This is even more devious than it first appears: there is a secret order of rogue elements elsewhere in the Fortress whom it is a good idea to tell you are from Analand.) Several encounters in the book can be simplified or bypassed entirely in this way, although there is one rather curious part where crucial information you need to win the game can only be found in a way that makes logical sense if you have the not-recognised bonus.
After you have gone so far in the adventure, you meet a character that calls you 'the Analander', and duly subtract 40 from the current section's number...









