The Abused Werewolf Rescue Group by Catherine Jinks

Tobias Vandevelde is a normal kid with normal, albeit rambunctious, best friends. So when he's found one night unconscious in the local wildlife park, he just chalks it up to a strange prank. But when a mysterious stranger shows up with his group of pale and sickly friends, Tobias starts to understand that there's something much weirder going on and he might be in danger because of it.