The common chestnut is, after seeing a movie: "The book was better."
Were there books you read because they made movies out of them?
I can think of two different takes on this question.
1) A book you read because you wanted to read the book before you saw the movie.
In my life, examples would be The World According to Garp and The Accidental Tourist .
2) A book you read because you saw the movie..
In my life, examples would be The Maltese Falcon, The Caine Mutiny, Anatomy of a Murder and To Kill a Mockingbird.