Stross Charles. Laundry Files 01. The Atrocity Archives

Ace Trade, 2004. 342 p.
ISBN: 0441013651.
Charles Stross takes a departure from his epic science fiction to craft this cross between Len Deighton — style espionage and H.P. Lovecraftian horror.
Bob Howard is a computer-hacker desk jockey, who has more than enough trouble keeping up with the endless paperwork he has to do on a daily basis. He should never be called on to do anything remotely heroic.
But somehow, he is.