http://www.amazon.com/World-Robert-...=sr_1_3?ie=UTF8&s=books&qid=1241038011&sr=1-3
Also referred to as The Big White book (BWB) or Small Black Book. Has info on the Age of Legends, Forsaken, Shadowspawn, the Nations of Randland and other lands like Seanchan, Shara and the Land of Madmen along with a world map and other stuff.
If you google "Strike at Shayol Ghul" you'll find a cool little story RJ wrote about the end of the Age of Legends.
-Sanderson talks a length about the split on his blog, it's enlightening and after reading it I understood better, even if I'm not totally pleased:
http://www.brandonsanderson.com/article/56/Splitting-AMOL
The book is only about half written (at 450,000 words!), split or not, we wouldn't get the ending until 2011. BS pulled off a remarkable feat by getting 450k words down in under a year, but he couldn't possibly keep that pace up.
-We couldn't know if RJ would have considered a split once he saw how big the book would become, he'd constantly underestimated how long this story would be from the very start.
His main wish was that the story be finished and he left more than enough written/typed/audio notes (there was a recording played at a conference a week or two ago of RJ describing the Prologue (just reading a description of RJ talking about it gave me chills)) and whole written sections as well as sitting his family down and telling them how exactly it was supposed to go.
-Tor are a business, they'll obviously want to make a profit. But you're kidding yourself if you think splitting this into 3 is going to cost much more than one volume at 8 or 900,000 words, one volume would cost a friggin bomb and be totally impractical to lug around (I've heard about Tor's shoddy bindings, it'd probably fall apart before you even reached halfway).