Re Tad williams: Yes, the dragonbone chair was the firs in the "memory sorrow and thorn" series. It was a trilogy, although the third book was split into two for some printings, so it is also a quadrilogy. It's basically a "re-imagining" of the LotR, with all (well, some) of Tolkien's attention to language, mythology and back-history, but with some cool new ideas, some deeper characters and obligatory "underground" chapters to satisfy Williams' fetish for being lost in endless dark tunnels. (Paging Dr Freud)Kinda cute in parts, but then so was the Tolkien stuff.
His newer series, Otherland, is better. That is kind of like fantasy/ quest stuff in a variety of futuristic VR settings. Very enjoyable, a largely believable and well researched vision of the future, although the ending sucks.
His other books that I know of are Tailchaser's song (Standard fantasy quest, but with cats instead of people. Not bad) and Caliban's hour which I haven't read.
Finally, check out
www.shadowmarch.com - he's publishing his newest book on the web. You get the first few chapters for free, then have to sign up for the rest. It looks pretty good.