Well, I just got to the end of The Road to Kotaishi, and I thoroughly enjoyed it. The immediate book I thought of was Lian Hearn's Otori trilogy, because of the Japanese slant on the fantasy; Kevin's book is very different, but I think it compares very well, and it's certainly equally thoughtful.
I guess it's a traditional quest fantasy with an eastern twist, the idea of a pilgrimage under the sacred Hakari lamp. The action starts moving from the first page, and the world unfolds with the characters and the action, without long swatches of back story. I saw a few traditional plot tropes coming (I won't say what, for fear of spoilers) but that didn't interfere with my pleasure in reading it.
There are lots of things I like: the metaphysics of this world made sense to me, and its unfolding morality, which is a nicely complex and I thought very human take on the old ideas (I use them too) of Light and Darkness. The world building seems thoroughly imagined. I found the different societies of Tonogato fascinating and I thought well drawn and differentiated: the traditional, ritualistic city of Hajimeshi, fallen on difficult days; the merchant city of Yutakashi; the religious fundamentalists of Shukyoshi, and the gender subtext there, all intrigued me; and I especially enjoyed the magical city of Tejinashi.
I thought the shifting between the different storylines was well handled; I found as a reader that I didn't notice them, just moving on happily to the next "scene", which I think is a good sign. The various intrigues and plots kept me interested, too. And lots of fascinating characters, who grow along the way; I liked Princess Mikasama's struggles with her ignorance, and how Shiko grew from an innocent as he encountered the outside world. Lord Itachi is especially vile, but most interestingly; I liked that he was, for all his decadence, an admirably brave warrior. And I'm very intrigued by the Voice, or whatever it is, that erupts in the text as (I presume) the Darkness: it's very suggestive, and there's enough of it, but not too much.
As for criticism (pedant time!

) - well, sometimes I thought the style became a little stilted, though never enough to be annoying: and sometimes there were words which I thought didn't belong in this world, being too contemporary - "lobby" and "foyer", for instance, make me think of modern hotels. (I'm especially aware of this sort of thing, because I've been picked up on it in my books by my very good editor). And I share Maus's reservation about some of the dialect dialogue. A little work with a red pen would get rid of all of those problems, though. They're very minor. So thanks, Kevin! It certainly kept me reading into the night well after I should have put my light out...