Untamed, by Kathleen Lawless

When Paris Sommer finds the secret diary of her great-great-grandmother, who ran an infamous bordello in the old West, her secret fantasies are ignited. Putting her librarian career to good use, she goes to Forked Creek, Nevada, to stay at the brothel and do some research. There Paris discovers a forbidden pleasure of her own: Mitchell Brand, a dead-sexy cowboy who knows just how to treat a woman — and make her beg for more. Brand's hard-lovin' ways welcome Paris into a world of passion she's never known...until a mysterious treasure map hidden in the diary leads them to a place where peril and seduction collide.