The Laundry Files are a series I am very fond of but haven't hesitated to criticize in the past. Basically, they're a combination of spy thriller, Cthulhu Mythos series, and office comedy. The strangest thing about that is such isn't even the weirdest part of the story as they also go in bizarre directions such as parodying vampires and superhero fiction. It's sort of an ad hoc Dreseden Files but, in many ways, even more peculiar.
One of the series' biggest strengths as well as weaknesses is Charles Stross refuses to let it fall into routine. Every book is a different genre and he has been known to switch protagonists as well. This is the second book in the series where Bob Howard, the nominal main character, doesn't appear at all. In this case, he's replaced by Alex Schwartz, the lamest vampire of all time. Alex was a rich twenty-something virgin banker before he became a vampire by discovering the secret mathematical equation for doing so. Now he's been dragooned into the Laundry at a 70% pay cut with his romantic prospects having gotten worse.
Alex and Peter, a local vicar, have been assigned to investigate various old Cold War bomb shelters in hopes of finding a new home for the Laundry after their last one was compromised by a hole in the universe. This results in Alex becoming entangled in an invasion of the British Isles by a race of elves. Yes, elves. It turns out the sidhe have been sleeping for the past few millennium and are fleeing their alternate Earth to try to take over ours. Humanity has been so busy preparing for the invasion by the Great Old Ones, they've completely screwed up prepping for a more mundane threat.
I've taken awhile to read The Nightmare Stacks because, bluntly, there's a weird coincidence here. Elves invading the British Isles and getting repulsed by the weird secret conspiracy government agency which protects the world is actually the plot of my upcoming Esoterrorism sequel, Operation: Otherworld. It's otherwise different from The Nightmare Stacks but reading this book was such an odd feeling I didn't know how to convey my thoughts.
So what did I think of this book?
Eh, it's okay.
The primary focus of the book is a romance plot between Alex and a elven agent who has stolen the memory and identity of a woman named Cassie before going native. Cassie is meant, by Word of Stross, to be a deconstruction of the Manic Pixie Dreamgirl archetype. In other words, a fascinating character who comes into the life of a boring schlub and makes it interesting. The problem is there's not really that much deconstructing.
Yes, Cassie is an agent for the Mein Alf-spouting elven empire but that's just combining the MPDG with that of the femme fatale who falls for the hero. Given Alex has almost no charisma by design, being a deliberately designed boring person yet "Cassie" falls head-over-heels for him, it seems like a strange thing to say the character is deconstructing anything. The romance, as a result, feels contrived and is probably the least interesting part of the novel. This is unfortunate as it's the primary focus of events.
The book has a large collection of interesting supporting characters, including ones which were formerly part of Bob Howard's but gradually drifted out of his pages. I'm particularly fond of "Pinky and the Brain" returning as the gay mad scientist couple are always a source of amusing anecdotes. The Dungeon Master is another great character, being a game theorist and strategist who puts everything in 1st Edition D&D terms.
The elves, themselves, are a decent enough opponent for the Laundry. They're only a tiny remnant of a once-vast civilization and hopelessly outclassed by the modern British military. They aren't aware of this, though, and their magic-based weapons system is actually better equipped to fight the Laundry than the people the Laundry are supposed to be protecting. The fact they're a despicable evil race (justified by the fact they're all mind-controlled from birth in a magical pyramid scheme) while also still having some measure of sympathy from the narrative is interesting too.
In conclusion, this is a decent enough book but not my favorite out of the series for a varity of reasons. The book changes the narrative of the Laundry-universe so is a can't-miss for fans but, otherwise, skippable.