The New Essential Guide to Alien Species is a 224-page reference book published by Del Rey, the thirteenth book in the Essential Guide series. It was written by Ann Margaret Lewis, who authored the original Essential Guide to Alien Species, and Helen Keier, a new-comer to Star Wars . The book was released on October 31, 2006 in America. It is noteworthy in that, though no species name or homeworld was given, the guide is the first to include information on Yoda's species.