Day 10: Favourite Tie-In/Game Fiction
Hmm. Not especially my thing, to be honest. I enjoyed a lot of the fluff in the tabletop Warhammer and Warhammer 40,000 books, and some of the novels, but that's not an RPG and other bits were less good or less to my taste. I've read some D&D tie-in fiction, but mostly because it's very accessible fantasy rather than in expectation of high quality. The games whose setting I enjoy most both started out as not-RPGs, sef Call of Cthulhu and Warhammer 40,000.
Honestly, I can't think of any contenders here.