Randall Hicks' The Baby Game.
Our hero is a young attorney/tennis pro named Toby Dillon. Since kindergarten, he has been best friends with Brogan Barlow and Rita MacGilroy, who are now married and Hollywood stars. They have asked Toby, who declined to work in his father's large law firm so that he could abide by his principles, to help them arrange a private adoption. Unfortunately, after the child is born, the baby is kidnapped and the birth mother disappears.
Toby tries to investigate on his own while cooperating with the police at the same time, and finds himself breaking a few little laws in the process. He also finds out a lot of information about his best friends that he's not sure he wants to know.
This is a quick, enjoyable read, and one can certainly imagine a movie coming from it. The sequel, Baby Crimes, is supposed to be due in June 2006, though it doesn't show up on amazon.com yet.