I nominate The Long Goodbye
by Raymond Chandler
I read all of Chandler's works 35 years ago, and this was my favorite. I'm looking forward to reading it again.
It is available for free here at MR:
Here are a few quotes from the Amazon page:
"Every time I finish reading one of Chandler's Marlowe novels, I end up feeling depressed, because it's one less Chandler novel that I can read for the first time. In my mind, he's that good -- he is one of the only writers that I am consistenly incapable of setting down to go to sleep... I finished the last half of "The Long Goodbye" at about 5:00 am -- I was so wrapped up in it, that I failed to notice the time."
"This epic Raymond Chandler novel is his most finely crafted and perhaps the best ever of its genre."
"I first read "The Long Goodbye" in 1976, before I had read any other Raymond Chandler novels. The book practically set off an explosion in my brain -- I have been fascinated by Chandler ever since. No other book by Chandler matches this one's emotional tone."