This is an interesting and surprisingly relevant concept piece, a near-term dystopia where convicts are housed within their victims house for maximum justice. As others have noted there are some flaws in the concept, but if you can suspend disbelief on some of the logistical elements of this new system there's plenty of story to get lost in.
There were parts where I was concerned some of the writing was slightly predictable, but there were plenty enough twists and turns to keep me engaged and I devoured this in a few short days.
Whilst tense at points, I'd query the 'thriller' label for The Captive, but I did enjoy how fleshed out the character of Jem became, fleshing out his backstory and making the story grittier.
This was a good introduction to Deborah O'Connor and I would certainly be interested in reading The Dangerous Kind now.