House of the Goat by A.P. Sessler

They were only following their average male instincts (and girls) when they wound up in the dusty parking lot, but the four young men find themselves guests at the mythical Casa del Cabro. When cult leader Anthony Aquarius makes an appearance, though, the boys are in for more than turndown service and wake-up calls.
Rituals.  Sacrifice.  Incarnation.
The hallmarks of Satanic Panic.
Master.  Dogma.  Followers.
The perfect recipe for a cult.
Sex.  Blood.  Magic.

Power comes in threes... as does terror, in the House of the Goat.