Z-Wave is a surprisingly complicated topic. This guide is comprehensive, and helped me to understand the underlying fundamentals which make it easier for me to understand what the "packaged" Z-Wave home automation systems offer. I've dropped one star, because there is a significant number of typos... it could have benefited from proof-reading by a native English-speaker.
If you a just purchased some z-wave gadgets and want to understand a bit more of this technology it's a good book to start with. All aspects of the standard are described, also other available standards are outlined. There are also some tips and tricks are also mentioned.