There's no movie I've ever seen that hasn't butchered the
book's plot and character development in an attempt to get it small
enough/simple enough for a film.

Treasure of Seirra Madre is clearly better than the book...and I love the book.
The film simply does what the book does faster and with sharpness. If a book
contains a great central concept, above and beyond it's characters, a good or
even superior screenplay can result. I believe in an economical writing style,
which is central in good screenwriting.

RB