The Atrocity Archives by Charles Stross (#1 of the Laundry Files series) is currently $1.99 in the US
https://www.kobo.com/us/en/ebook/the...ity-archives-1
https://www.amazon.com/Atrocity-Arch.../dp/B000OIZUIA
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 for some reason, he is.