Most people consider the two bases for the movie "I, Robot", which were a book with the same title and another called The Caves of Steel, to be better than the movie... although I wonder how many of them have read them and how many are repeating the refrain about the book being better because everybody knows that's just what you're always supposed to say.

I have just about given up on written fiction, because most authors have verbal habits that annoy me (not due to grammar error nit-picking, but as a matter of style) or make their writing too much of a personal soap box. I consider writing to be the superior form for conveying non-fiction information, and video to be the superior form for telling stories. So I don't have a lot of examples of book/movie overlap that I've personally experienced both forms of.

But one that does stand out to me is The Lord of the Rings. His more anthology-like stuff and short stories are great, but Tolkienn was absolutely awful as a writer of novels, blathering on and on about things that just don't matter to his own characters and story, stretching out a small things as if to meet a page-count quota and then going back to drop more extra things in between them as if after finding out that despite all the stretching he still hadn't met the quota, seeming to change his mind several times about what kind of story to write and its big overall themes as well as the little details but then not going back to clean up the contradictions and aimlessly meandering tone switches... ugh. Other than almost any movie scene with Arwen in it, the movies were mostly a matter of Jackson fixing things Tolkienn had screwed up.