Matthew Sturges' Midwinter, and Office of Shadow

Amazon calls The Office of Shadow a sequel to Midwinter, but going by the blurb, they don't seem to share characters.

Can someone shed a bit more light on the relationship of the two books? Without any major spoilers, please.

General comments on the books would also be appreciated. Did you like (either one of) them, and why?

Reading through the descriptions on Amazon, I'd say they are related by universe but not true sequels as it were.

I've not read the books myself, but that is my opinion.