Hot Blooded by Kendall Ryan

I’ve pretended to be human for a century. Surely the next month shouldn’t be a problem?

Reign Tryst is a vampire, and like most vampires who are of a certain age, ahem, give or take a century, he’s grown bored. Restless.
He’s been there, seen it all, and little excites him anymore.
Except… the very off-limits, very human young assistant he hires to curate his personal library, Tressa Porter. Long-dormant feelings he hasn’t felt in ages spring to life. How very curious!
He’s never needed anything like the sudden and demanding need he has to taste her.
Reign has a life-or-death decision to make—deny his instincts and send her away, or satisfy his cravings, and hope he doesn’t destroy the one thing he holds most precious of all.