In A Lonely Place is one of the few films that nearly equals the novel upon which it was based. The novel of the same name, by Dorothy B. Hughes, is a masterpiece and quite daring for the time, the 1940s. Hughes compares quite favorably with James M. Cain (author of Mildred Pierce, Double Indemnity, The Postman Always Rings Twice) and in many ways surpasses him as a writer of noir. Her character development exceeds Cain's, in my opinion.
I highly recommend picking up a copy of Women Crime Writers - Four Suspense Novels of the 1940s. Not only do you get In A Lonely Place, but also, Laura (another wonderful film), The Horizontal Man, and The Blank Wall. There is another volume, but Suspense Novels of the 1950s. If you want both, I believe a box set is available.
I don't want to give away the novel or the film--though you'd think a novel from the 1940s and a film from 1950 should be fair game. But I've found so many people today haven't paid the classics any mind and that's a real shame. The novel is actually much darker than the film and ultimately heartbreaking and tragic (the film is also heartbreaking, but in a different way).
Criterion (I've gushed over Criterion products before on here and on social media) is releasing In A Lonely Place on 5/10/2016. Criterion Blu-Rays are more expensive than other Blu-Rays, but if you're a film buff there are no better versions to buy. The films are restored versions and always have plenty of extras.
While the film deviates from the novel (it's a very loose adaptation), it doesn't take away from the novel. They're both equally enjoyable and tragic. So noir.