Since I had to set a finish date for this book I set it to today (the date of review). To be honest, I've not finished it. In some sense it's a book not meant to be "finished" since it can also be used as a reference work (although this potential use is negated by the fact that XMPP has great online docs and resources).
It's long winded in places and the O'Reilly XMPP book is more fun to read and better written.
Nevertheless, if you do want to use Javascript with XMPP then this is chock full of examples.