Mercy just can't help but get in trouble. When a lone werewolf shows up on the doorstep of her car repair shop, Mercy finds it within herself to help him out...until he ends up dead. In finding his killers and bringing a massive plot down, Mercy finds herself caught up in events that are far beyond her powers and totally out of her control.
Patricia Briggs is merciless (no pun intended) with her characters -- you never know what's going to happen to them, or if they'll make it out alive.
To call this book engaging is to do it a severe injustice; I picked it up two days ago and read it and the next three books straight through, forgoing sleep in the process -- I was so thoroughly hooked I honestly couldn't put any of them down.
Mercy herself is an INTERESTING character. Totally deserving of capital letters, too. She's like Anita Blake without the Mary Sue complex -- totally more realistic and easier to identify with. I especially love the fact that Mercy has a history degree, so she's working as a mechanic -- a situation I can totally identify with, having a history degree myself.
If you like urban fantasy, this is totally worth the read.