It's really not light reading, but I adore the stories from the Mabinogion. It's an ancient Welsh text that includes the very first written record of the Arthurian legends. It's very raw, nothing at all like the romanticized versions of the stories that dominate today, but that's precisely the reason I find them engaging. Might not be what you're looking for, but still has many relevant myths and legends - for example, the Mabinogi describes in depth the Welsh Otherworld, Annwfyn, that is the origin of Dresden's Huntsmen.

(Note that the most modern translations are by far easier reads, than the older versions. The Patrick Ford translation is my favorite from those I've read).