Poison Ink — Christopher Golden

SAMMI, TQ, CARYN, Letty, and Katsuko are floaters. None of them fits in with any particular group at Covington High School--except each other. One night, to cement their bond, the girls decide to get matching, unique tattoos. But when Sammi backs out at the last minute, everything changes. Faster than you can say "airbrush," Sammi is an outcast, and soon, her friends are behaving like total strangers. When they attack Sammi for trying to break up a brawl, Sammi spies something horrible on her friends' backs: the original tattoo has grown tendrils, snaking and curling over the girls' entire bodies. What has that creepy tattoo artist done to her friends? And what--if anything--can Sammi do to get them back? This deliciously creepy psychological thriller is the perfect summer read.