I love Sam Peckinpah, but the movie version of The Getaway seemed completely flat after reading the book.
I devoured everything that Black Lizard re-published by Thompson in the early 90s. You should check out some of the lesser known books. He falls prey to re-using character mannerisms at times but they're all worth reading; A Hell of a Woman is one of my favorites.
I've never seen the movie, actually, but I can't imagine them filming the ending as written!
Hell of a Woman is on my list, and so is Savage Night. But I might take a break and switch to Agatha Christie next.
You also might want to try some of the Travis McGee books by John McDonald. They're not gritty and dark like Thompson but they're entertaining.