The book’s narrator is a school kid named Wade Watts, whose parents at least had the foresight to give him the alliterative name of a superhero. But Wade’s real circumstances are not exciting. He lives in a tall block of stacked mobile homes and escapes to an abandoned van to adopt his online persona. He goes to school because he has to; his video console and virtual-reality visor will be taken away if he flunks out. But his school avatar is often seen slumped at its desk, sleeping. That’s because Wade is busy being an alter ego called Parzival. Like Art3mis he spells his name funny because the other spellings are already taken.

Wade is obsessed with “Anorak’s Invitation,” not least because there’s something fishy about it: the extras seen with Halliday have been digitally borrowed from old John Hughes films. There’s no knowing what actually happened to Halliday. But Halliday’s knowledge of 1980s trivia was so thorough that Wade is determined to match it. (As a full-time gamer he is competitive by nature. And what else has he got to do?) So he knows everything about every episode of “Family Ties” and every coin-operated arcade game. “Ready Player One” takes its title, sentimentally, from the phrase that signaled the start of games from that era.

In “Anorak’s Invitation” Halliday mentions one of his sentimental favorites, the Atari game Adventure, and the Easter egg that its creator, Warren Robinett, incorporated into it. And now it’s time to start looking things up, if you are hooked by Mr. Cline’s premise but unfamiliar with his huge frame of reference. An Easter egg is a secret sign or clue or whatnot that may be embedded in a game, and Halliday has deliberately created an occasion for egg hunting. A great many egg hunters, known as “gunters” for short, do nothing but try to find Halliday’s eggs. Reader, ask yourself: Would you be interested in Wade’s story if you weren’t sure he was smarter than all the other guys?

Because Wade needs at least a few friends, he bonds with Art3mis and three other avatars. They become known as the High Five when they start racking up high numbers on the cosmic scoreboard. Mr. Cline describes their progress with a winking appreciation of the culture clash that ensues when Wade, a humble schoolboy, reaches the Tomb of Horrors to lock antlers with Acererack the Demi-Lich from Dungeons & Dragons. But “Ready Player One” crosses a line here, when its virtual-reality fetish leads it into Dungeons & Dragons for real.