When a movie is based on a book, it often doesn’t turn out exactly how readers see it in their brains. Does the movie ever spoil the book for you? If so, which book? Is there a movie that enhanced the book for you?
The movie doesn't usually ruin the book for me. If I don't like the film, I may be annoyed with what they did to the plot and characters, but that just makes the book all the more special to me because nothing can outdo it. If I don't like the film, then I just dismiss it, and stick to the book.
Some films have enhanced my enjoyment of books, however, as they sometimes make it easier to visualise. One example is 'The Road'.
For me, movies normally don't ruin the books they are based on but the opposite can happen quite easily. If important events are changed or left out, I tend to get miffed. The things that normally get me is often if a book is really long, events will be glossed over or omitted. This makes the movie hard to follow or feel disjointed.