The listing, Shadowmarch: Volume I - Paperback has ended.
Having read everything by Tad Williams to date, I have come to the conclusion that he does best with epics, be they fantasy or sci-fi. 2003's _War of the Flowers_ left me a little cold, as did his breakout debut, _Tailchaser_. His Otherland and Memory, Sorrow & Thorn sagas, however, are some of the most satisfying reads you will ever avail yourself of.
I won't rehash the plot; that's been done plenty elsewhere. What I will say is that Williams take familiar elements and does wonders with them. His plotting and pacing are relentless, compelling you to read more in one sitting than is good for you.
The only thing I could have done without was one character's time underground, which reminded me a bit too much of Simon's escape in _The Dragonbone Chair_. But that comes late in the book, and by then you'll be hooked.
If you're looking for some excellent fantasy while waiting for George R.R. Martin's _A Feast for Crows_, this is just the thing.