The Atrocity Archives
by Charles Stross
Bob Howard is a computer hacker desk jockey, who is looking to move up to field work while avoiding bureaucratic hassles. He works for "The Laundry" an X-files like government organization charged with stopping any occult summonings. It turns out that some higher mathematics can lead to the ability to summon vile maleficent things from beyond.
Bob's mission is to stop people from using this arcane mathematical knowledge, whether accidentally or deliberately. It's A fun cross between the office and a spy novel and Lovecraftian horror. The overall tone is witty and comedic not horrific.