The Otaku Encyclopedia is an encyclopaedic dictionary of about 600 Japanese terms mainly from the Otaku subculture. It includes slang, jargon, characters, creative people and companies, and the like.
The main areas covered are manga, anime, cosplay, figures and dolls. Associated areas such as video and tabletop games, or airsoft guns, are also briefly mentioned.
Each term is fully explained with its original Japanese katakana and/or kana.
There are also frequent mini essays or interviews on some of the main personalities of the subculture, such as maid cafe idols, big name otaku, and figure sculptors.
As far as my knowledge goes this is all accurately explained. The author is an otaku-journalist, who having lived in Japan for about five years, is pursuing a PhD in otaku culture at the University of Tokyo. While I can't claim his depth of knowledge, my association with Japan goes back over 15 years. Although not an otaku myself I have been following Japanese and anime/manga culture since the early 1980s.
So I recommend it. If you want to know what "tsundere", "moe" or "gokko asobi" means, this book will tell you. It will also work as a general overview of the otaku scene.
If I have an argument with this book, it is the presentation of otaku as a part of Cool Japan. Good anime is cool. I don't think otaku is cool. Although otaku love anime, otaku itself is mainly a mode of consumption rather than self-expression or creativity. It does not have a cool image in the west, and much less in Japan itself. While the 2005 movie "Train Man" started to rehabilitate the image of otaku, it still remains a slightly weird subculture, especially on the outer fringes.
Some aspects of otaku -- cosplay, maid cafes, "dollpla" and "doujinshi" -- undeniably have a camp charm and demonstrate creativity and active fun.
The fetishisation of pubescent girls as sex objects, nude printed dakimakura (hug pillows,) and various kinds of sex dolls and figurines, will never be cool. It feels a bit creepy. It seems a small step from that to the pervy sarariman, groping schoolgirls on rush-hour trains and stealing housewives' panties off the washing line.
A major area of genuine cool is the Harajuku based street fashion scene, portrayed in magazines and books such as Fruits. This is only peripherally part of the otaku culture, via photography and fetishisation, for example, of schoolgirls' loose socks. It isn't covered here, which isn't a criticism as you can easily get other material covering it.
The book is an excellent introduction to the otaku subculture. I am left with the feeling that it is as much an attempt to claim public space and validate the author's personal interests, as it is a celebration of a successful cultural movement.