I'd like to do a twist to the topic:
Usually film adaptations of books are worse than the original book, but what happens the other way around? I mean book adaptations (novelizations) of films.
I've read eight novelizations (the six Star Wars films plus the Clone Wars movie, and Indiana Jones and the Temple of Doom -the old one by James Kahn, not the new one that appeared when The Kingdom of the Crystal Skull was released), and I think that mostly are cheap merchandise, although they add new scenes that aren't on the movies (mostly scenes that are on the original script but were cut from the final edition).
The only book I trully think that is way better than its movie is Episode III: Revenge of the Sith