A Book of Tongues, Volume 1 of the Hexslinger Series

Two years after the Civil War, Pinkerton agent Ed Morrow has gone undercover with one of the weird West's most dangerous outlaw gangs-the troop led by Reverend Asher Rook, ex-Confederate chaplain turned hexslinger, and his notorious lieutenant (and lover) Chess Pargeter. Morrow's task: get close enough to map the extent of Rook's power.