I'll Give You the Sun by Jandy Nelson

Jude and her twin brother, Noah, are incredibly close. At thirteen, isolated Noah draws constantly and is falling in love with the charismatic boy next door, while daredevil Jude cliff-dives and wears red-red lipstick and does the talking for both of them. But three years later, Jude and Noah are barely speaking. Something has happened to wreck the twins in different and dramatic ways…