Haven't finished the book yet so can't comment on how helpful it is. My rating is based mostly on the ass-poor production quality. Typos abound on every other page; sentences are not just dangling, they're not even finished, captions refer to non-existent photographs, and illustrations are applied to the wrong subject. That's just annoying and insulting to the reader (what, we're not supposed to notice?). Come on dudes, pay attention and proof your work, please.
And to be honest, the writing's not that great, either.