Wicked lovely by Melissa Marr.
Not too explicit, idk, I haven't read it in a while. There's a love triangle between Ash, Keenan and Seth.
Well, kinda a square..
Ash with Keenan because of destiny.
Ash with Seth because of love.
Keenan with Donia because of love.
A couple of my favorite authors are Katie Macalister (Sex and the Single Vampire, Sex Lies and Vampires, Crouching Vampire Hidden Fang, Zen and the Art of Vampires, In the Company of Vampires [These are just her vamp books, she writes about other paranormal things, too. Just look her up]), and Charlain Harris (The Sookie Stackhouse novels that True Blood is based from.)