Liar by Justine Larbalestier  

Micah is the ‘after-school’ girlfriend of Zach Rubin—who has a ‘real’ girlfriend at school. No one else knows about their relationship. Both are excellent runners, although, again, no one knows this about Micah. She hides the truth about herself and lies all the time.

When new at school, Micah pretended to be a boy, then a hermaphrodite. She seems to have family members that don’t exist. She says her dad is an arms dealer. And wait until you hear about the purposes of her bedroom furnishings. As she is caught in one too many lies, no one believes anything she says anymore. So when Zach is found dead—apparently brutally murdered and mutilated—the police start to question her. Micah says she’s going to tell us the truth—the ‘before’ and the ‘after’ the murder.

But Micah can’t stop lying. And you never know what to believe. Just as you think you have the story straight, there’s a new twist and it all falls apart. You’ll end not knowing if you’ve unraveled the lies, not knowing if there is a supernatural element at work in the murder—just not knowing anything. But you’ll race through the suspense, desperate to get inside Micah’s head.

Fast, fun, full of surprises. One of my best summer YA reads.