The Apocalypse Codex, by Charles Stross
This fourth book in Stross's Laundry series is, apparently, like the previous ones, written in a pastiche of some other author's style, but this time it wasn't one that I recognized. It's also a damned fine read.
Many series get tired after a while, as the characters stop developing or worse, develop into one-dimensional archetypes. This doesn't happen here. We learn and see more of both the characters and institutions. We also have a well-developed antagonist, one who is (of course, this is a Laundry book) utterly evil, but for the best of reasons and thinks he is on the side of the angels.
However, I feel that the ending was rather rushed and not particularly believable. No sensible bad guy would leave one half of his Doomsday Device utterly unguarded, especially when he knows that the opposition are in the field. And the idea of the double double-cross and subtle but quick manipulation by the Black Chamber of institutions and individuals is frankly silly. For that I deduct one star. I'd deduct more except that the rest of the book is so gloriously fun to read, deftly combining horror, action and comedy as we have come to expect from the series.
I recommend this book, provided that you have read the previous installments. If you haven't, then you should read them first.