I finished The Atrocity Archive by Charles Stross this morning.

As is stated in the book in both the introduction and the postscript, The Atrocity Archive is a cross between Len Deighton and H.P. Lovecraft. It takes a fairly generic idea, a secret gov't organization that deals with the hidden magical nature of the world, but portrays it with the feel of a classic spy novel.

The closest comparison is Tim Power's Declare. Powers attacks it from a more historical point of view, illustrating the history of the cold war with a mystical component, while Stross creates new stories without many references to real events. Both are good books, but in very different ways. Stross has a more light hearted, almost parody, feel while Power plays it very straight and serious.