Yes, if you're interested in Tad Williams' works, Memory, Sorrow and Thorn is a must. I just loved it! I have read it in German and English and only the second time around I got what the title meant! (But that's just me!) Don't worry I'll let you discover that by yourself!
If I may say so, it's one of his best works! And a stand-alone trilogy, too, as far as I know. (That's the good thing about Williams. He sets out to write a trilogy and that it is...)
Well, I'll stop rambling and will let you start reading!
