I only know the author from her novel inspired by (or tie-in to, if you're ungenerous) the game Ico. This felt weirdly like a tie-in to that; a great deal of the book's imagery reminded me strongly of either Ico or Shadow of the Colossus. Not the story, mind you, that's new. But when you start with a cursed nameless land and a giant tower in the middle, with nameless robed monks scurrying around, you wonder.
Anyhow. The main story involves Yuriko, a schoolgirl in contemporary Japan. Her older brother disappears after apparently going nuts and stabbing two classmates. This is straight-up realism, as shocking as it sounds -- including the reactions of Yuriko's own classmates.
The author waits a beat, and then introduces a talking book to give us back the comforting veil of heroic fantasy. Yuriko's brother has been seduced by an ambiguous story, the archetype of the Hero (if good) or the King in Yellow (if evil). On either side, it is the fantasy of the powerless everyman taking control of his destiny. Which is exactly what heroic fantasy is, so maybe that veil isn't as comforting as we thought.
Yuriko is quickly handed great magical powers and a new name (U-ri the allcaste); she is dispatched to an imaginary land (yes, as in fictional) to follow and perhaps save her brother. She is accompanied by a cute mouse (nee dictionary) and a nameless boy monk. Also by a ton of further ambiguity. Everybody, but everybody, keeps secrets from her. Sound familiar?
There is lots of adventuring, lots of scenery, lots of horrible monsters and semi-trustworthy allies, and at the end... a very qualified victory. It's exactly what a fantasy novel promises. But.
...The ontology is hard to get hold of. We get lot of discussion of stories and how they affect the world; it's all faintly obscure (or obscured by translation issues? "Allcaste", for a start, I have no idea what to make of that word.) We are introduced to a lot of history of the fictional world, the Haetlands; some of it is thrown at us quite late, and being fictional, are we supposed to take it at face value? I'm not sure. Everything seems to be wrapped up in a tidy knot at the end; the nominal moral is to not try to live your life as a story. Don't be a hero! ...says the fantasy novel. I am suspicious.
It's a good read. It falls short of a compelling read, for me; I took several breaks for other books. But then, I finished it. I truly do not know what the author was getting at, and I look forward to reading other people's commentary.