I love the premise of "Blood Work": FBI agent Terry McCaleb had to leave the agency, not because he cooked a fall, shot somebody, or angered a superior. Simply, he was dying.
One night, his transplant pager goes off, alerting him that a donor heart had become available. He had his transplant, and was taking it easy on his boat. Until one day, a lovely young woman named Graciela shows up on his boat, begging him to look into her sister's murder. McCaleb protests that he's retired. Then, the young woman plays her trump card: her murdered sister's heart was now beating in Terry McCaleb's chest.
Being retired, McCaleb has no official sanction, no jurisdiction. But he sniffs around a little, and starts to see things the detectives working the case had missed. Naturally, he gets more and more involved, as he moves closer to solving the murder.
I liked McCaleb, as well as the supporting cast. The book felt a little long to me, and it used early 1990's technology (dial-up modems, pagers, etc), but these are extremely minor complaints in a truly interesting novel. Recommended.