The 20th Victim by J. Patterson and Maxine Pietro

 20th Victim is the latest in the Women's Murder Club series. A skilled sniper (or maybe more than one) is taking out drug dealers from all walks of life and the San Francisco police are having a hard time stopping him/them. That's the basic Lindsey plot. (Her husband Joe is off in Napa trying to help an old friend whose father has just died under somewhat murky circumstances.) Medical Examiner Claire is dealing with a serious health issue. Yuki the ADA is reluctantly prosecuting a teenager who was the driver in a crime that ended up with the death of a cop--but he won't say who his boss is (out of fear of his life), which is frustrating Yuki no end because she doesn't really want to charge him alone for all the crimes. And Cindi the crime reporter is dealing with a smarmy upstart at her newspaper who wants her job.

It's a good summer read featuring familiar, likable characters. You don't really have to have read the earlier books in the series, you just have to know that Lindsey, Claire, Yuki, and Cindi are really good friends.