I feel for authors whose books are made into bad movies

I don't know, in a lot of cases its probably the only way the author will get some serious money. And a lot of films are based on little-known works of presumably little merit. You pretty much expect the film to be worse than the film, so it irritates me more when a book's reputation is lifted by it being associated with a film of rare quality, like The Godfather, or to a lesser extent, The Shining.