Disclaimer: This review was written before the much more enjoyable second series of Torchwood was put on telly and addressed many of the issues I had with the show.
I should point out, that while I watched Torchwood all the way through, it was more in the hope that it would all come together at some point than because I was really enjoying it. So why read one of the books? Well both Andy Lane (who wrote Slow Decay) and Dan Abnett have proven themselves fine writers and I approached Border Princes as a Dan Abnett novel instead.
So I was mildly surprised (though not that surprised) to find that Dan's novel presented the version of Torchwood I'd been expecting and hoping for. A group of paranormal investigators, normal people, who deal with crimes using alien artefacts and incursions from other realms. The interactions between the team, which I'll admit don't mirror the television show that well beyond the first episode, make you feel like they're a good team, as opposed to the backstabbing, callous bunch of cheats and liars the show featured. When watching the show I could never understand why they all kept working together when they would shoot each other, bully each other etc. Captain Jack particularly feels closer to how Russell T Davies writes him than what we saw in the show and is a lot easier going and willing to share his mysteries.
The writing is well paced and quite gripping. Even though you'll probably see where it's all going, it's a pleasant trip getting there. There's plenty of humour and the relationship writing for Gwen is particularly strong, even if Rhys does get short shrift (but then Gwen had an affair with Owen in the show, so why should we believe her relationship with Rhys is particularly strong). James, the mysterious new Torchwood member, is a nice chap too.
If you're a big fan of the show, it isn't quite so faithful as you might hope, I guess. And it is hard to figure out where it fits into the timescale. I'm tempted to suggest it may fit better in the second series, depending how that turns out. (Edit: And whaddayaknow? I was right!)