Another book that some people might like if they enjoyed Rivers is The Atrocity Archives by Charles Stross.
There are some differences - it's contemporary fantasy-horror, with a branch of British security services (codenamed the Laundry) dealing with the supernatural. It has a Lovecraftian threat, Dilbert-style office politics and humour, and is written in the style of a John le Carre Len Deighton spy thriller. There is a fair bit of computer technobabble (the magic system is based on advanced mathematics).