The book of Bo Broussard (the half-demon owner of a supernatural-only club) and of Nyx (a beautiful waitress who we have just found out in the previous book that she is a demigod). 
 Sex is the only way Bo can tame his half demon self, but Nyx doesn't have any experience. 
 We also have the first family of half demons in the series. It is time for Bo to meet his relatives, which at least they are kind of normal for half demons. 
 Nyx's family on the other hand is a bit psychotic. 
 Nyx's fae prince father is determined to marry her to another fae without asking her permission. Or Bo's permission as a matter of fact. 
 As Drake said 
 "Bo clearly does not know how to act around his female. Once he figures out how to, they will be mated soon." 
 Nyx's lunatic goddess mother for unknown reasons will send Nyx and Bo at a Hell realm where they will need 
 -to sort out their relationship (Bo will act like a caveman in some hilarious situations), 
 -to survive (fighting scorpion-hellhound creatures, avoid bluish-green, horny demons, combating Koighans, i.e. Inbred half-demons) and 
 -to find an exit to the real world (two unexpected males will help them). 
 Arya the mother of Petronilla clan proves to be a tough cookie in this book and saves the day, while at the same time friends like Drake, Victoria and Finn will also help. 
 Overall a great robust addition to the series! 
 The world becomes a more complicated place with the addition of new species, new hybrid species and new realms.