The second Quarry book, where he gets out of the situation he ended in the first one. I haven’t been able to read the first one yet, so I’m just assuming it was bad. I like these books, they’re quick, enjoyable reads.
Spoiler, I suppose:
The whole central part to the mystery is that the girl he meets and the object of the other hitmen is the Broker’s wife and they’re after her because of the relationship and he only meet’s her because of Quarry’s relationship to the Broker. Max Allen Collins’s original publisher decided to retitle the book, The Broker’s Wife. That completely ruins the mystery. It’s still a good book despite that, but such a clueless thing to do.