Equinox

Brennan is the only mate Sarayana will ever want.  Sadly, though, he's a human, and she is a dragon trapped in her reptilian form. 

Sara can only change shape into a human body once a year, on the night of Ostara when the Goddess is said to return to her maidenhood—on that night and that night only, Sara will finally have the chance to be one with the man she loves.