You're probably so cool that you heard of Donald Westlake, like years ago. He sure does seem to have a lot of books out, and he does seem to get mentioned sometimes in the same breath as Elmore Leonard, Charles Willeford, Jim Thompson, etc. Which is to say, he writes crime novels. Not detective novels. Novels in which people commit crimes.
I have read ten of his books in the last eight days. They're that good. He's got two major series. I started with the Dortmunder novels, which are about a hard-boiled thief whose capers always go ludicrously wrong. In one novel, for instance, they conduct a heist in an office building, only to discover that the megacorporation that's based there is in the middle of an orientation session for the army of private mercenaries they've hired to overthrow the government of a small Latin American nation.
His other major series is the Parker novels, which're about a hard-boiled thief who's an emotionless monster and who always wins, no matter what the odds are. Apparently the Dortmunder books were Westlake's humorous take on the Parker novels, and they bear a lot of similarities. It's like they take place in slightly askew universes.
Weirdly, given how much I tend to like comedic novels, I actually enjoy the Parker novels more. They're shorter, and they tend to be much more high-concept. For instance, in the one I just read (The Seventh), a heist goes awry when an angry ex-boyfriend stumbles into Parker's hideout, trying to settle a score with the girl that Parker's sleeping with, and ends up killing her and making off with the money. The whole novel is Parker's focused attempt to throw off the cops and find the ex. Another, The Outfit, is about Parker trying to fight an entire organized crime syndicate that's decided he's crossed it. In the current book I'm reading, The Score, Parker assembles a group of twelve men, and they rob an entire town in North Dakota.
Parker is so terrible. He's a sociopath, but he's not even cruel. All he wants is money. During most of the year he picks up a woman and goes with her from resort town to resort town. When he runs low on money, he gets involved in these heists and steals more. He doesn't kill except when it's the best solution to his problems (this tends to be unfortunately often), and he's willing to torture and kidnap people too (there hasn't been any rape yet, and I don't think there's going to be). He's chillingly evil, but a very different sort of evil from what we're used to. He's the sort of evil that is greedy and has no moral code of any sort. If he had different appetites, like an appetite for fame or for dominion over other people, he'd be a real monster. But since all he wants is money, he's sort of tolerable.
The books are great though. And Westlake does this thing about halfway through each one where he cuts for a few chapters into somebody else's mind, and these are my favorite parts, because it's clear that he's writing Parker this way because that's how the character is. Westlake himself is capable of broad range and a lot of nuance (although let's be real, his female characters are infrequent and thin, though the Dortmunder books are better on this than the Parker books, and I've literally only seen one nonwhite PoV character in the course of these ten books). Anyway, I highly recommend.