Lydia Chin is an American-Born Chinese who lives in New York City's China Town with her widowed mother; Bill Smith is an Army brat and one time bad-boy. Together, they are the most interesting pair of PIs I've had the pleasure to run across in maybe ever.
Every successful mystery series has a gimmick; in Rozan's case, the gimmick is that she has two quite different main characters, and her books alternate viewpoints between them. In Lydia Chin's outings the plots center around the Chinese community in New York, and Bill Smith helps her out. Bill Smith's tales are more traditional private eye novels, with Lydia Chin providing legwork and color. I tend to prefer the Bill Smith books, but both are outstanding—and my favorites in the series are the Lydia Chin books Shanghai Moon and Ghost Hero.
In Shanghai Moon Lydia is tracing the history of a legendary piece of jewelry that dates back to WWII-era Shanghai, and the history of the people who owned it: a Jewish refugee from Austria (did you know that some Jews fled from the Nazis to Shanghai?), a Nationalist general, a German officer in disgrace, a secret supporter of then General Mao. Ghost Hero takes place in the world of contemporary Chinese art, and harks back to the days of Tianamen Square. Both of them kept me up late.
But the eleven Lydia Chin/Bill Smith books are a lot more than pair of loosely related mystery series, and that's entirely due to the chemistry between the two characters. They aren't lovers; they aren't dating; but everyone assumes that they must be. In fact, Lydia Chin and Bill Smith are a couple in every way but the actual.
It's not for lack of trying on Bill Smith's part; it's clear from the first book that there's no one in Bill's life other than Lydia, and there isn't going to be. But it's to no avail. You see, Lydia's mother was born in China and wants her to marry a worthy and prosperous Chinese gentleman and give over her disreputable profession. She hasn't a single kind word to say about Bill Smith, who is not only not Chinese, he's not prosperous, and his profession is equally and identically disreputable.
But then, slowly, you learn that dear old Mom's just the excuse. Old Bill has some serious baggage that we learn about very slowly over the course of the series. He's committed to Lydia but he can't open himself fully even to her, and she's not going to settle for less than that.
Mind you, that's never said in so many words; neither Lydia nor Bill are inclined to obsess verbally about their relationship. But it's there, and it's a pleasure to watch it evolve over the course of the series.
Highly recommended. The first book is called China Trade; you should check it out. (H/T Julie at Happy Catholic.)