Nothing More than Murder, by Jim Thompson, 1949. Here's a novel about a movie theater proprietor in the 1940s, a troubled marriage, and a scheme to murder a woman and make it look like an accident. It's noirish as all hell, and dark as the hearts of those who scheme in the darkened theaters of this book.
This is a typically great Thompson novel, with several features that give it a lot more depth than you might expect in a story like this. First, the intricate, cut-throat machinations behind the movie theater business in the 40s is very esoteric and replete with specific lingo (a glossary is provided). Secondly, the notion of narratorial unreliability is used here to good effect to mislead the reader as to what is going to happen; and certain details of plot are only given in flashback to further warp the timeline. What seems like a simple story quickly becomes quite complex. The third is that this is as much a mystery of psychology and character as it is of plot, and the story in the end turns out rather differently from where we thought it was going. As the narrator's schemes and his self-confidence unravel, his carefully planned reality runs off its course like a film that has run off its spool.