The background premise of the series is that magic is real, but that it's a branch of complexity theory. And if humanity makes too much psychic noise we will wake sleeping aliens, the "elder gods", who will eat us all. The Laundry has to defend humanity both from this and from other less total threats.
In The Fuller Memorandum Howard confronts cultists who want to wake the elder gods in order to negotiate with them, while fending off Russian spies with their own agenda. The plot is that of an espionage thriller, decorated with occult and IT devices and a bit of historical back story (involving the brief and brutal rule of the White Russian von Ungern-Sternberg over Mongolia).
If the plot elements are a mix of John le Carré and H.P. Lovecraft, the feel is more Terry Pratchett. The Fuller Memorandum is a comedy, with nothing taken at all seriously and a lot of amusement derived from the interaction of magic and information technology, and from the workings of British civil service bureaucracy.
Stross' Laundry series is pretty content-free, but it makes for pleasantly frivolous entertainment. If this sounds like it might be appealing, you can try it out through several short stories set in this universe which are freely available online — "The Concrete Jungle" is probably the best place to start.
- Related reviews:
- - more science fiction