Black Halo by S.L. Naeole

While nearly everyone else at Heath High is preparing for prom and graduation, Grace Shelley is coming to terms with the end of her relationship with Robert, the angel who saved her soul, her life, and then broke her heart. It's not easy, especially when she can't escape his thoughts.

But Grace has other things to worry about. Like her friend Stacy's cancer, and her best friend Graham's ex-girlfriend, whose attacks on Grace and her friends only seem to escalate with each passing day. And then there's Samael, the Archangel of Death, whose own death after his last attack on Grace had been revealed to be nothing but a lie.

When Samael tries once again to finish what he started, Grace finds herself having to rely on Robert for help, something that forces the both of them to confront the lies that exist between them. But, as Samael closes in on not only Grace, but also on the people she cares about, she learns a secret that forces her to make a decision that changes not only her, but the very world she lives in.