Shadowmarch by Tad Williams
I got all four of these books for Christmas, and blew through them. Excellent, though the last one felt as if it was hurried into print (things a once-over should have caught, like an event occurs where you know someone is not present, and that someone later reports on the event as if they were there, someone spreads out a map on their lap when they are standing, etc...). I'm wondering now about his other series and how they compare to this one - any thoughts?