Tell It Again: Adapted Screenplay, 1973

I find this to be one of the hardest categories to adjudicate. Since we're talking previously-published works, there's reasonable doubt as to what belongs to the original author, and what belongs to the adaptor. I'm familiar with none of these books, so I have no inkling of the writers' fidelity to their source materials. How much is their own dialogue? What plot twists did they invent? What was thrown out to accommodate the world of cinema?