I got this book not because I wanted to play the RPG, but because I wanted more information on the aliens, tech and worlds of Babylon 5. Well the book doesn't really deliver all of that, but it does deliver some. As a rule of thumb any Babylon 5 gaming resource is not considered official canon according to show creator J. Michael Straczynski. However this book does get one thing accurate, and that's the races.
So one section of the book gives you some pretty detailed information on the major alien races from the series, and that info looks pretty spot on when compared to more official references. This is pretty much the only reason I have to endorse the book for my needs.
I'm a fan of the show so enjoyed this book. The rules look workable but I was mostly interested in the history and stories that it presented as examples.