Warbound / Larry Correia.

Enhanced descriptions from Syndetics:

Book Three in the Grimnoir chronicles, and sequel to HardMagic and Spellbound . Only a handful of people in the world know that mankind's magic comesfrom a living creature, and it is a refugee from another universe. The Powershowed up here in the 1850s because it was running from something. Now it is1933, and the Power's hiding place has been discovered by a killer. It isa predator that eats magic and leaves destroyed worlds in its wake. Earth isnext. Former private eye, Jake Sullivan, knows the score. The problem is, hardlyanyone believes him. The world's most capable Active, Faye Vierra, couldback him up, but she is hiding from the forces that think she is too dangerousto let live. So Jake has put together a ragtag crew of airship pirates andGrimnoir knights, and set out on a suicide mission to stop the predator beforeit is too late!