The victim is a medical physicist who'd been killed execution style.
It's quickly discovered the victim had access to large quantities of radioactive cesium. Normally cesium is used in the treatment of cancer; in the wrong hands it could be used in the production of a dirty bomb.
The FBI are instantly involved since this case could have a terrorist angle to it. Predictably there is tension between them and the LAPD. When Homeland Security becomes involved mistakes begin to happen caused by inter-agency rivalries.
I've always found Connelly's writing to be an easy read, having been a crime reporter for the LA Times he has the ability to make a story flow. This book first saw publication as a serialized story in the New York Times Magazine which explains the low page count. There is very little time given to the struggles of just being Harry Bosch that is usually found in one of his books.