This heart of mine

"Seventeen-year-old Leah MacKenzie is heartless. An artificial heart in a backpack is keeping her alive. However, this route only offers her a few years. And with her rare blood type, a transplant isn't likely. Living like you are dying isn't all it's cracked up to be. But when a heart becomes available, she's given a second chance at life. Except Leah discovers who the donor was -- a boy from her school -- and they're saying he killed himself. P...