(I got an ARC courtesy of NetGalley, in exchange for an honest review.)
This is only the second Doctor Who novel I read. In the meantime, I managed to catch up on a lot of episodes I hadn't seen (including the ones with the Twelfth Doctor); it was a good idea, since otherwise I would have had less clues about who the characters were, especially when the Paternoster gang was concerned. Unfortunately, it was therefore also very easy to realise that they weren't that well-portrayed, at least not in my opinion. Hadn't I watched the most recent seasons, I would've likely been confused; having watched them, I don't recognise many people in here. I guess Strax felt the closest to how he behaves in the series, but then, he may have been the easiest one to grasp as well.
I'm particularly miffed about the way Vastra and Jenny were handled. Vastra's supposed to be the Great Detective, the one who inspired Doyle to write Sherlock Holmes's adventures, and yet her role was completely stripped off meaning; she didn't get to do much, looked like she was here mostly to get into trouble and then saved, and this doesn't sit with me as far as she's concerned. Not a word about her relationship with Jenny either, which I found odd. This applied to several characters, in that I couldn't get a strong grasp of how they factored in the mystery, except to get into trouble (and only the women in this story happened to get into trouble and need saving; I don't recall Strax or the Doctor doing the same). As for the Doctor, he didn't feel and act much like the one I got to see in the most recent episodes. Clara was just insipid. At best they all were bland, at worst not true to their selves, cast in damsel in distress roles, and not allowed to unleash their full potential.
The plot was somewhat interesting. I liked the first half, for the atmosphere woven through the Carnival, and the way the mystery started to unfold. I liked it much less towards the end: nice twist, though predictable, but muddled. (Also, two characters get together without any serious apparent reason; while somewhat cute, it was useless, especially with the other relationships in the story not mentioned or developed.)
Conclusion: 1.5 stars. Mildly enjoyable as a quick read while travelling, yet totally forgettable in the long run, with characters that have little to do with who they are on TV. (And the point of reading a novel based on a TV series, to me, is to find the themes and people I liked in the show, after all...)