I watched the movie, and since it was produced by Disney and directed by Spielberg, I know it was made family-friendly and I expected the book to be more edgy. I wasn't disappointed. While the movie is enjoyable, the book is much better, more adult oriented and with way more "retro" trivia of video games and movies. The characters are the same, but the major events are quite different. Cline says because he used way too many copyrighted references in the book, which would cost a fortune to obtain rights to show on screen. Also, all characters in the book are much less pretty, all being overweight and Wade being completely hairless, from top to bottom.
There is no race for the first key, instead it is a dungeons and dragons game that is found on the planet Ludus where all public schools are and playing a game of "Joust" (classic video game from before my time, never played it). The first gate opens by doing full "flicksync" of the movie "War Games" playing as Matthew Broderick, having to know the full dialogue. The second key has to do with the legendary "Zork" video game and the 1983 classic SciFi "Blade Runner" and the gate is opened by playing the 1987 game "Black Tiger" (another I've never played, slightly before my time as a gamer). Wade also plays a perfect game of PacMan with the maximum obtainable High Score, which awards him an extra coin.
The third key is hinted by a song from the Canadian band "Rush" and their concept album "2112" and the thirds gate is the actual Castle of Anorak that Halliday used as an HQ while alive. Of course the "IOI" are always following Wade, trying to kill him (they kill his aunt and everyone in the stack vertical where Wade lived), and also kill Daito, one of the "High Five" who were first at the top of the Scoreboard. Not funny and not for kids.
There's a battle for the Third Gate, and the top players, including Sorrento with his Mechagodzilla, and just when Wade is about to win, IOI detonate doomsday device which destroys the entire planet and everything on it. However, the Pacman coin Wade won gives him an extra life and he enters the third gate where his plays character in the classic movie "Monty Python and the Holy Grail" and obtains the easter egg from the early video game "Adventure." Wade wins and shares his winnings with the other 3 remaining of the "High Five". Also loses his virginity to Artem1s.
The book is a joy to read, especially if you are a video game (and movie, and space rock) geek, and get all or most of the bountiful references. I am ready to read the sequel "Ready Player Two" although I've read that it is not as good as the first book.