Some book-to-movie adaptations really don't do justice to the book, but I thought Ready Player One did, despite all the changes.
Two factors may account for this result. First, Cline understands that what works on the printed page may not work as well on the screen. (Some of the tests on the way to the victory work when you're reading about them but wouldn't adapt well to the screen. Playing a video game against a lich wouldn't be that exciting--but a race around obstacles like Godzilla and King Kong? Much better!)
Second, Spielberg was smart enough to involve Cline in the screenplay. (I had forgotten this, but Spielberg did the same thing with Michael Crichton on the first Jurassic Park movie.
These two factors together account for a movie which differs wildly in detail from the book but retains its spirit.