Unyielding Autumn by Heather Relken

With no memory of how or when she was abducted, Autumn finds herself sold at an auction to a beast that has trouble reining in his bloodlust. When his fangs fixate on her friend and then begin to turn to her, too, Autumn has little choice but to trust the midnight-black alien that helps her take down the beast.
Even if it means getting blood on her own hands.
Coming to terms that she’s falling in love with a bona-fide extraterrestrial takes less convincing than she’d expected, but she’s not clear of the danger yet–and just when she starts to feel safe, she’ll find there are still beasts lurking.
THEY’VE HAD A TASTE, AND WANT MORE.