Hard Magic — Larry Correia

A HARD-BOILED PRIVATE EYE -- CAUGHT IN A SECRET WAR OF MAGIC.

Jake Sullivan is a war hero, a private eye -- and an ex-con. He's free because he has a magical talent, being able to alter the force of gravity in himself and objects in his vicinity, and the Bureau of Investigation calls on him when they need his help in apprehending criminals with their own magical talents. But the last operation he was sent along to help with went completely wrong, and Delilah Jones, the woman the G-men were after, who just happened to be an old friend of Jake's in happier times, had a lot of magical muscle with her, too much muscle for the cops to handle, even with Jake's help.

It got worse. Jake found out that the Feds had lied to him about Delilah being a murderer as well as a bank robber, and they had lied about this being his last job for them -- he was too valuable for them to let him go. And things were even worse than Jake imagined. There was a secret war being waged by opposing forces of magic-users, and Jake had no idea that he had just attracted the attention of one side, whose ruthless leaders were of the opinion that Jake was far too dangerous to be permitted to live . . .