Switching from one genre to another is always a tricky proposition, especially if you and your readers might be at odds about what genre you’re writing in. The Nightmare Stacks is the 7th book in the Laundry series about a secret British government agency fighting occult threats, only that as of this 7th book it’s not secret anymore.
There are two kinds of urban fantasy settings (very generalized), the one where the supernatural world is hidden (Dresden Files for example) and one where its out in the open (Anita Blake series). In my experience, few urban fantasy series have depicted the point of transition (the recent Magic ex Libris Revisionary is one example), and the deeper reason for that is that most of them are, despite the urban and modern element, fantasies.
They are not interested in looking at it from an sfnal point of view, showing the effect that these revelations have on the culture, on people and how it shapes society. In my case, if I want to see these kind of stories, I rather go directly to the source, to science fiction that actually deals with things not based on magic or the supernatural.
One could argue that Stross laid down the rules of his setting from the beginning to be like science fiction, to be internally consistent, but at the end of the day it feels as real as PSI-based powers or attempts to scientify magic ala midi-chlorians, which might look good enough for some, but it’s still not the same as science fiction that deals with rather more ‘realistic‘ things.
So, why is changing your genre a tricky proposition? Because it might be that readers dig your stuff for entirely different reasons than you where expecting. Or maybe not. It does look like the Laundry series is in endgame mode and most people who are still with the series might hand around for the ending just to see where it lands, but to say that I like where its going would be a lie. Changing genre means focusing on different aspects than what drew me to the books in the first place, and it doesn’t really work all that well here.
One example is that The Nightmare Stacks contains long, very drawn-out sequences of what I can only describe as war- or combat-porn, detailed, long-winded descriptions of weapons and battle scenes that make the second half of the novel rather tedious and which feels completely at odds with earlier novels in the series and what they focused on. And while I do like the inclusion of Moorcock-style elves invading Britain much more than the silly and really annoying superheros in the previous book, it was much better for the lack of those boring fight scene and weapon descriptions.
Will I hang around for the next few novels in the series? Sure, but I’m less enthusiastic about the prospect of Stross looking at the ramifications of putting the supernatural in the spot-light, while diminishing the aspects of the earlier books that I actually enjoyed.