Even if you have no intention of ever sending players into the astral plane, this book is an absolute must have for the detailed look at githyanki society. The githyanki and githzerai have always been very interesting races so it never hurts to get more information about them. Aside from that, the book is still pretty good. It's nice to have a book that portrays the astral plane as something other than an empty void that connects the outer and prime material planes. It gives the requisite info on how to get around and such as well as detailing the "dead gods" that are mentioned from time to time in other Planescape sourcebooks. All interesting stuff, but I can't imagine that I would want to set a series of adventures in the astral plane. The githyanki, however, I can use anywhere, which certainly makes the book worthwhile in my eyes.
[5 of 5 Stars!]