Iron Kissed by Patri­cia Briggs, pub­lished Jan 2008, is the third book in the Mercy Thomp­son series, pub­lished by Ace.
VW mechanic, Mercy Thomp­son, is a shape shifter. She is a walker who shifts from human to coy­ote at will.  In the world that Mercy inhab­its, the were­wolves, fae and vam­pires exist along­side humankind. 
How­ever, the fae and the were­wolves have been some­what forced