City of Windows by Robert Pobi

 This is the first in the Lucas Page series, which I have been reading out of order. We learn more about Lucas's back story and how someone recognized that this little foster kid was a genius and decided to help him. The main story is about a skilled sniper who is taking out law enforcement under very difficult circumstances. Lucas is brought in to help the FBI figure out where the shooter is shooting from (using his mathematically-oriented mind and logic). He's also trying to help the FBI figure out who the shooter is and what the motive behind the killings is. Then Lucas himself gets on the sniper's radar.

I like these characters: Lucas and his wife Erin, Whittaker (the hard-driving, mind-reading FBI agent assigned to Lucas), and his FBI boss Kehoe. I think there's one more in the series that I have to track down. Good read.