Hey, check out the cover! Unusually sordid, even by my standards. [Update, September 2022: you'll have to trust me on that. Image no longer available at Amazon.]
OK, so I didn't like Don Winslow's recent novel Savages very much, but as fate (implemented by the Perl script that picks books out of my to-be-read pile) would have it, this book de-soured me on Winslow for now. It's Winslow's first novel, published back in 1991; it's also part of a series featuring the character of Neal Carey, sort of a private investigator.
Neal has an unconventional background: raised fatherless by his junkie prostitute mother, he's relatively feral until he rips off the wrong guy: Joe Graham, a one-armed, height-challenged PI. Joe becomes young Neal's mentor, schooling him in the ways of shadowing, searching, creeping, and research. But Neal also has his own interest in classic British Literature, and (as the book opens) is also a graduate student working on his degree.
Joe and Neal are provided their assignments by "Friends of the Family", an organization run as a sideline to a Rhode Island bank. It is dedicated to pulling the chestnuts of its ultrarich clientele out of various fires. In this case, Allie, the wayward daughter of Senator Chase, a prospective Vice-Presidential candidate, has gone missing. Allie is in her late teens, and already has a long history with promiscuous sex, booze, and drugs. Neal is tasked with finding her, and getting her presentable enough to appear as part of the smiling happy family at the upcoming convention.
This takes Neal to London, where (as it turns out) Allie has fallen in with an unusually bad crowd. As the cover implies, it's all quite sordid. But definitely readable.
Consumer note: as I type, Amazon only has the Kindle version for a reasonable price. Which is what I read; unfortunately, it's shot through with what appear to me to be typos, errors in capitalization, and missing/extra/wrong punctuation. But it's cheap!