In an alternate future children can be sold by their parents on their 15th birthday to offset their cost of living. Bran is one such child, and has spent the past 3 years being mistreated as a sex slave by various owners. He is sold to the slave breakers who train young slaves and retrain difficult slaves.
Warning: This story does contain graphic sexual scenes of a man on man nature. As well as hinted at scenes of sex with under 18s. I can't say that I was expecting this kind of thing to happen in the book, but despite the graphic nature, and me being female, it wasn't overwhelming. You can't have people being sold into sexual slavery and skirt around sex, which this author didn't. Also the way the story itself (as in the bits that weren't sex) was well written and the characters were engaging enough for it to be detracting.
I only know that the setting was contemporary because the blurb says so, there was no way to really tell this from the story itself, also there was no real world building or background as to why parents are able to sell their children.
Saying this the characterisation was good, the household really felt like a family, which seemed to be the point of the relationships. But ultimately all of the people that are slaves didn't actually seem to be treated or even act like slaves. This even goes for Bran who had 'bad' masters before entering Holden and Alix's house, he seemed to start to trust very very quickly, which doesn't seem that to seem really realistic.
Note: I have put bad in annotation marks, not because I believe that there can be good masters, but simply because I don't believe that the concept of slavery allows for there to be good masters as the 'mastery' of other people is fundamentally bad.