The Kane Chronicles: The Serpent’s Shadow by Rick Riordan. Book Trailer.
Under the cover of darkness, the serpent waits, watching for the right moment to strike. She stared into the hypnotic eyes, drowning, thoughts scattered. The serpent’s eyes were compelling, raw, pulling secrets from her soul. It tried to merge with her mind, become as one. It was terrifying, and yet, she couldn’t stop it. When foster teen, RACHEL LARK is sent to camp, she plans to run away. But the city girl is unprepared for what she encounters in the woods, a terrifying serpent. As Rachel looks for help, she finds camp leaders aren’t what they seem. Now Rachel will face the evil changeling using survival skills she never knew she possessed. For deep within the Serpent’s lair, Rachel will come face to face with the beast from her nightmares.