We've all seen the movie, right? Well, the novel lends some interesting background to Norman's story. (Actually, the backstory is used in Psycho IV: The Beginning - cut me some slack, I watched in the Olden Days when you had to make due with what was on TBS to while away a Saturday afternoon!), and made much clearer to me Mary/Marion's motivations. It's also just a fun, quick guilty pleasure of a read.
Bloch's story is a weird collision of pop psych freakshow, character study, and Columbo-style murder mystery, with a soupcon of salacious material that probably had many boys hiding this under their mattresses in the '60s. But mostly it works, driven largely by Norman and Lila's characters. Like the film, the book wraps up with the odd doc-splaining of Norman's history and condition, which falls pretty flat, but being in Norman's head for much of the story is equal parts intriguing and repellent - but always interesting.
Definitely recommended, and the audio book was very well done - the reader does a great job at presenting the characters and accentuating the tension in the story.