We meet our protagonist, Gregorio Rivas, as he's performing a gig in a popular bar in Ellay (L.A.). He's got a decent living, considering he's living in a broken society with no advanced medicine or even the rudiments of transportation and electricity. A local bigwig offers him an obscene amount of money to go back to his former profession of redeemer, someone who kidnaps members of a widespread cut, deprograms them, and returns them to their families and friends. Rivas tries to turn the job down, because as a former member of this particular cult, he's susceptible to their tactics. In other books he's written, Powers introduces an element of something so far out of the ordinary that it could be called supernatural. In Dinner at Deviant's Palace, it's an alien with an unusual ability to not only feast on other sentient beings, but also to make its snacks love it.
Rivas does accept the job and what follows is a dementedly entertaining and nail-biting journey through the remains of the Los Angeles metropolitan area. There are animated trash monsters, hive minds, displaced souls, mutants, cultists, bicycle gangs, and an army from what remains of San Bernadino. This book blew my mind.