The Laundry books started as pastiches of spy thrillers and then went into urban fantasy. In a way The Labyrinth Index has come full circle. It is an out and out spy thriller, albeit one cloaked in the trappings of Stross’s Laundry. Lovecraft-styled fantasy, now rapidly dealing up towards eleven - the series is probably at about six right now - and taking just enough inspiration from recent political movements in the anglo-world before being twisted into non-euclidean angles.
It’s a Mhari book. Mo is mentioned, Bob has a couple of lines in a scene you can just about not realise it is even him. Stross has posited that the Laundry has grown sufficiently that he can take the Pratchett approach. That is, multiple semi-separate series with their own casts that occasionally cross over and plots that reference each other. I can’t recall if Stross has ever expressed the idea, but lately I have wondered if he ever regrets her early characterisations. Yes, it’s all from Bob’s perspective, an at-the-time callow jerk and unreliable, but all the same. She’s considerably more three dimensional now. I really enjoy the non-Bob perspectives and I am glad we now see Bob and Mo from the outside.
I’m less enamoured of the out right adaption of the Nyarlathotep and Cthulhu, but it’s personal taste. I like it Lovecraftian, not “Lovecraft was a weirdo who knew some things that happened to be real”. Although I am amused how Stross - almost certainly - lampshades that his “Real Cthulhu” is inspired by what creeps him out.
If you’ve heard of this book it’s probably because you’ve read all of the preceding books. You should totally read this book. If you haven’t read the earlier books in the series, you should try out The Atrocity Archives first, knowing it was intended as a one-shot, and then read The Jennifer Morgue knowing it is a slight reboot. If you enjoy those two, you will want to read them all.