It's been long enough since I last reported a free e-book out of Tor that I can't help but think I missed one (or two).
Anyway, Tor's got another one out there. This time we get to take a look at Charles de Lint's Spirit Walk. From the post:
Charles de Lint’s Spiritwalk (1992) is the sequel to Moonheart, his groundbreaking novel about the people in and around a house in modern Ottawa that straddles this world and another one. Here is the same cast of characters, as they deal with a pair of very different threats to the ancient house. As in Moonheart, de Lint skillfully combines a contemporary sensibility, a great sensitivity to the rhythms and patterns of myth and folktale, and a set of simply likeable characters whose lives you find yourself wanting to hang out in.
From the post's comments it appears while this is a continuation of a pervious novel, it does stand enough on its own that it is not required you read Moonheart. I imagine like any pseudo-series, where at least the world and some of the characters appear in both works, having read the previous novel will enhance the experience but not having read won't necessarily ruin it.