One point five stars, since I actually finished this book and because there are some good bits in it. But there are also bad bits and OMG-WTF?-BBQ bits and even sappy bits in the end. Both the main characters and the book have multiple personalities, it seems.
The first half of the book requires Olympic grade Suspension of Disbelief on several occasions. But I can suspend me some disbelief when required, so whatever. But once the kitty-killer is killed and Sin goes on his emo binge, the plot starts staggering around as gracefully as a wounded grizzly who just won't keel over and die already. Not only do we have to suffer through the massively worn out I-am-no-good-for-him-so-I-must-leave-him-for-his-own-good vehicle for separation of the main characters, but in the process we get bombarded with extraneous..... stuff. Who cares about bondage fairy pendants, sweet 16 birthday parties, Trev's search for a successor, Collar Club rules, squid mates, etc? Never mind that we get not one, but two hospital reconciliations! And a kidnapping! And a wedding! And an Alien Invasion! Ok, sorry, no Aliens.
Someone get this guy an Olympic level editor, because there is potential here none the less.
P.S. When I think of 'Indulgence' I think of quality chocolate, expensive single malt or a day at a spa. Not being beaten into a bloody pulp while getting fucked. But that's just me.