Top critical review
Reviewed in the United States on March 27, 2015
I have a weird child-like fondness for the WoT, the first volumes of which I read as a kid, and this is an interesting and well-written supplement to the series. It illuminates some of the details and logistics of the philosophy, magic system, and cultures of the WOT books in an clear, engaging way. Since RJ was involved, I think a reader can reasonably take the content here as canon, if you will.
On the other hand, the book has two major weaknesses. One is that is was compiled and published mid-way through the series -- so it is far from comprehensive. There are things I was curious to look up in this book that simply aren't there, because they didn't exist in the series itself yet. (A more comprehensive encyclopedia edited by Jordan's wife is due out late in 2015, I believe.)
Two, is that the art is pretty god-awful. And that's coming from someone who actually kind of *likes* the mass market paperback cover art for the series. If you think that art is bad, this is far worse. It's sort of embarrassingly poor.
So in short, this is okay -- if you're a fan and you can get it cheap, I'd say go for it. Otherwise wait for the newer reference due out soon.