Moon called, book 1
Patricia Briggs et David Lawrence2011

Mercy Thompson inhabits two worlds without truly belonging to either. To the human inhabitants of the Tri-Cities she's an oddity, a female mechanic operating her own garage. To the town's darker residents, werewolves, vampires, and fae, she's a walker, a last-of-her-kind magical being with the power to become a coyote.
Mercy warily straddles the fine line dividing our everyday world from that darker dimension... 'till a boy, mauled by vicious werewolves and forever changed by the attack and on the run from those who committed the crime, appears at her door. Now her two worlds are about to collide! Outnumbered and out-muscled, can Mercy possibly save the boy... or even herself?

Titre original : Moon called, book 1 (2011)