Issue 92 of the Anime News Network's magazine, Protoculture Addicts, includes a tremendous review of The Anime Encyclopedia, Revised and Expanded Edition: A Guide to Japanese Animation Since 1917, by Helen McCarthy and Jonathan Clements. The massive, definitive book came out at the end of 2006; but, given it's density, reviews are only now coming to the cultural forefront.
Protoculture Addicts gives the book 4/5 stars (!), noting that this vastly updated edition includes "over 250 biographical notices and studio entries....This type of information is really helpful, since the Anime Encyclopedia is the first English-language anime reference to include it. Whether you are simply curious or heavily involved in anime, this book is a must!"