Angel's Honor — Erin M. Leaf

Raphael had no idea what he was getting into when he went to Castle Archangel to study the People's oral history. He didn't expect his wings to suddenly change from brown to the purest white -- the mark of an Omega, the destined mate of the Alpha. There has never been a male Omega before, not in all the millennia angels have flown the skies of Earth. However, when Raphael meets ebony-winged Gabriel, the true leader of the People, he knows he wants this man more than anything. Change is not always bad.

When Gabriel's wings suddenly turn to startling ebony, he must deal with the knowledge that he is an Alpha, a leader of the angels. When he discovers that his destined mate is a man, he must accept that being Alpha of the People means accepting more than he'd expected. When their current leader challenges him, accusing Gabriel of committing one of the People's most dishonorable crimes, Gabriel must fight: for his honor, for his mate, and for the survival of the angels.