I really enjoyed The Witch Roads, by Kate Elliott. The depth of the worldbuilding is a delight, and the vibes are exquisite -- it feels amazingly real, full of history and old traditions and cultures. It's a little slow for a modern novel (which I don't mind); it reminded me of an older book, in terms of quality (The Fortress in the Eye of Time by C. J. Cherryh) that I also loved. It's the first book in a duology, so I really need to get my hands on the second book.

As to the story: to protect herself and her nephew from a local lord with an ugly grudge, a courier gets sucked into helping an obnoxious prince take a dangerous route to bypass an avalanche and deal with an urgent, secret mission. The mission gets complicated when said prince ends up possessed by a haunt from ancient ruins; and of course, the courier has her own secret to keep...