I've read this book a few times now; and each time I glean some more info that I had missed earlier on. The book is very adaptable, and has vital information whether you are playing about with some haXe/flash or doing some heavy neko - all in this book is as well written and as versatile as both haXe and neko.
It's also worth noting that this is one of the few dual authored technical books I've read where both authors styles match each other well; their knowledge and enthusiam for the subject shines through on every page.
If you are doing (or considering) any haXe or Neko, then this is the book for you - in fact, even if not it's very interesting from a technical standpoint to see just how versatile a language can be when you target multiple vm's with a single syntax.
It is really well written and accessible for non native. Thick, dense and comprehensive, in every page I've learned something. Chapters can be browsed to fetch necessary info without having to start from page one, use cases are smart. Content goes beyond your usual flash/web related book. I'm really enjoying reading it.