This ranks among the best horror I've ever read. Though there were elements that felt dated, it held up remarkably well for having been written more than 50 years ago. I found myself wishing I didn't already know the twist! (As an aside, some would probably suggest I put that last word in quotes, thinking it's so obvious, but I think much like the identity of Rosebud in Citizen Kane, it's just not that well-guarded of a secret in pop culture. Hitchcock's adaptation was so influential that folks know about specific scenes, whether they've seen the movies or not, and there have been enough variations on the twist that it nearly feels like a trope now.) 
 The writing and construction of the novel, however, pushed this above and beyond for me. Psycho is concise, well-paced, and not a scene is wasted. Very impressive. 
 I was also reminded a bit of Joyce Carol Oates's Zombie, though that's a more straightforward story just from the serial killer's point of view. Both are short novels where the authors explored a contemporary serial killer; Bloch's was based on Ed Gein, Oates's on Dahmer.