Fwiw I liked it. Very stream of consciousness like shah said, but there are quite a few nice insights into Yohji's design & thought process and philosophy so if you are interested in that and are using it as a gateway into his mind, you could definitely do worse. It is not a "fashion book" as such though. Instead of twitter I would say it is like compiling a lot of tumblr posts on Yohji interviews and quotes into a book. That could be the height of inanity and pretension, but it could also be interesting if you like that sort of thing.
Check out the pdf on the thread (first post has a link) and see what you think.
I also have "Japanese Fashion Designers" and that's not bad. Been looking for books on Comme des Garcons but never have any luck. Where are you getting yours shah (please don't say eBay)?