The book is an excellent resource. I've done my fair share of rigging, and Allen and Murdock have put together a body of information that not only teaches me new tricks, but polishes and streamlines what I already do. Body Language will be the first place I look when I need to dig around for rigging assistance.
Body Language has me excited to rig again, which is perhaps the greatest aspect of the book. There are a lot of little "aha" moments here, and I'm itching to put them to use. It's an essential component of my reference library.
I have only one complaint with this book: It doesn't cover 3DS Max. It's understandable, what with Maya being dominant in the high end of the field, but some of the principles and techniques here are so good, it just seems a shame to not have Max involved. Ironically, then, it's the excellence of the Maya coverage that leaves me wanting the same for Max. Perhaps there's a sequel in the works.
That minor quibble aside, I still rate this at the full five stars. The book stands on its own merits, and that I wish for more merely testifies to the value of the data.