Every Last Word by Tamara Ireland Stone

Accurate depiction of mental illness is often hard to come by in teen fiction, but Stone's depiction of Purely-Obsessional OCD is spot on. Samantha "Sam" McAllister fit in right away: athletic, popular, pretty. But she struggles to hide her illness from the snobs she calls friends, second-guessing herself and worrying she'll slip up often. When Sam meets Caroline - a girl who may be her polar opposite - she is shown a world she'd never thought she'd enjoy. The impeccable details bring each character to life, giving others struggling with debilitating illnesses a place to belong and those who aren't a whole new level of understanding.