Another Day David Levithan.

A girl falls in love with someone who wakes up in a different body each morning in this enthralling and poignant follow-up to the New York Times bestseller Every Day. David Levithan (co-author of Will Grayson, Will Grayson with John Green) turns his New York Times bestseller Every Day on its head by flipping perspectives in this exploration of love and how it can change you. Every day is the same for Rhiannon. She has accepted her life, convinced herself that she deserves her distant, temperamental boyfriend, Justin, even established guidelines by which to live: Don't be too needy. Avoid upsetting him. Never get your hopes up. Until the morning everything changes. Justin seems to see her, to want to be with her for the first time, and they share a perfect day--a perfect day Justin doesn't remember the next morning. Confused, depressed, and desperate for another day as great as that one, Rhiannon starts questioning everything. Then, one day, a stranger tells her that the Justin she spent that day with, the one who made her feel like a real person . . . wasn't Justin at all.