The Sky is Everywhere by Jandy Nelson

Seventeen-year-old Lennie Walker, bookworm and band geek, plays second clarinet and spends her time tucked safely and happily in the shadow of her fiery older sister, Bailey. But when Bailey dies abruptly, Lennie is catapulted to center stage of her own life—and, despite her nonexistent history with boys, suddenly finds herself struggling to balance two. Toby was Baileys boyfriend; his grief mirrors Lennies own. Joe is the new boy in town, a transplant from Paris whose nearly magical grin is matched only by his musical talent. For Lennie, theyre the sun and the moon; one boy takes her out of her sorrow, the other comforts her in it. But just like their celestial counterparts, they cant collide without the whole wide world exploding.

This remarkable debut is perfect for fans of Sarah Dessen, Deb Caletti, and Francesca Lia Block. Just as much a celebration of love as it is a portrait of loss, Lennies struggle to sort her own melody out of the noise around her is always honest, often hilarious, and ultimately unforgettable.
(From the YouTube description)
Publisher: Dial (March 9, 2010)