Ready Player One is referred to as sci-fi, which isn't surprising as it takes place in the future and inside a video game. But there's at least as much reason to consider it a fantasy novel, in more than one way. The novel is a pretty standard quest in its structure. In the future, the OASIS virtual reality MMO is so popular that it's supplanted the real world for much of humanity, including uber 80s geek Wade Watts. Wade's obsession with a decade long before his own stems from a contest put forth by OASIS' creator James Halliday. Halliday, who grew up in the 1980s, made his will into a contest. Whoever could find the hidden Easter egg embedded deep within OASIS would get his fortune. And the clues are all related to 1980s pop culture. (Maybe it's bitterness due to having been born only two years before that decade ended, but the 1980s fanboying didn't quite strike a chord with me. But it is important to the book that the focus be on the 80s, and it's quite cleverly done.) Anyway, to get to the Easter egg, egg hunters (known as gunters) must find three keys and solve puzzles behind three gates. It's so very RPG. Obviously Wade finds one of the keys, and before he knows it he's in the spotlight and in the race for the egg. Along the way he gains allies and finds romance, all the while opposing the dastardly IOI corporation.
Besides being modeled after a basic fantasy quest, the book is also nerd wish fulfillment fantasy. It's what every teen/twenty-something male nerd wants: adventure, validation for devoting his life to meaningless trivia and skills, the love of a woman, money, power, etc. But while I recognize this, I also commend Ernest Cline for writing in Wade a truly likeable protagonist and a very well-rounded supporting cast. Plus, the OASIS is freaking cool. And this book has the most realistic portrayal of the whole "save the world in an online game" setup I've ever seen. It's hard to have tension and suspense when it's avatars at stake, not human lives, but since OASIS is such an integral part of the world and having your avatar killed loses you everything, including levels and items, and since the conflict is brought into the real world as well, the dramatic stakes are satisfactorily high.