Lou Ford is a small town deputy sheriff in Texas doing his best to keep up a friendly veneer, though all the while he's struggling with the sickness inside him. The sickness, of course, is that he's a sociopath, and a violent one at that. But what I didn't expect was just how sympathetic Thompson makes Lou at the start of the book (of course, it's written as a first person account, so maybe it's Lou making Lou seem so sympathetic)--but Lou really does seem to be trying to be good at the start, trying to keep everything under control. He still needs to lash out occasionally, but prefers to do that verbally rather than physically. He almost got put away as a kid for killing someone and he doesn't want that again.
Then a situation occurs, and Lou has to take care of business, only there are those who see through his facade and suspect him from the start. As in all good noir novels, the more Lou tries to cover his tracks and throw off the scent, the deeper into it he gets, and the more things start to unravel until, near the end, Lou hits you with the truth. He wasn't trying to keep his sickness under control. He was never in control.
Thompson's writing style is spare; there's nary a description of anything or anyone. He also hints obliquely at certain events rather than informing the reader outright, which can be frustrating but jibes well with the conceit of the first-person account--Lou wouldn't necessarily want you to know that he might have been sexually assaulted by his family's housekeeper when he was just a kid, but he does want you to know something happened back then that shaped him, and here's a few hints. You put the pieces together.
First published in 1952, The Killer Inside Me hardly seems dated outside of a few references to politics and one character talking about "the negro problem." In terms of an exploration of the criminally warped mind, though, Killer still feels fresher than any mass market paperback original serial killer police procedural being churned out today. I think that's because Lou Ford isn't a criminal mastermind the way so many serial killers are portrayed to be in today's popular fiction. Thompson understands that Lou Ford needs to be relatable to be at all interesting, and so he makes Lou as average as you and me. As one character says in the novel, "A weed is just a plant out of place," and that suits Lou Ford to a tee.
The Killer Inside Me is more than just a crime novel written by one of America's best known crime novelists, it's also a great work of literature. This novel wouldn't be a weed on anyone's bookshelf.