Ava is a firebug, one of the lesser known beings of the paranormal world. She essentially has the awesome power to start and then control fires. While the power may be great (and rare) it has also gotten her into a contract with the Coterie, which is essentially a magical mafia (and her contract's out clause is basically death or more painful death). Venus, the head of the Coterie, uses Ava as more or less a hitman. Not thrilled with her current job position, Ava does what she's asked, learning as little about her hits as possible, and then trying to live some small semblance of a normal teenage life with her guardian Cade - she's even managed to find herself a normal human boyfriend. Things begin to unravel though when said normal human boyfriend unknowingly (?) takes her to a restaurant/club that serves as the Coterie headquarters and Venus uses the opportunity to give Ava a job she has no choice, but to refuse. Venus doesn't just accept refusals though, and now Ava and her friends (and other magical creatures, such as were-hares they find along the way) are on the run.
Firebug is a paranormal book that employs sarcasm and quite a bit of tongue in cheek when discussing the paranormal universe. It's high on action, friendship, and loyalty and low (though not completely bereft of) on romance. McBride clearly enjoys paranormal worlds, but doesn't take it too seriously. While I thought her other book Hold Me Closer, Necromancer was more humorous, Firebug definitely held my attention through the end.