Now, if you're not familiar with it, Bön is the native "shamanistic" religion of Tibet, that strongly influenced the way that Vajrayana developed. I suspect that I picked this up at the NYC Kalachakra just to get some info on the Bönpo traditions. Frankly, though, I have a hard time really separating what's in this volume with the general stuff I've been exposed to of Vajrayana teachings. Perhaps Bönpo has become so intertwined with the Tibetan Buddhist lineages, that it has become something of a "heretical" close cousin, something like Sufism to mainstream Islam. Most of the materials that I can find on the web refer to it as the "Bön Buddhist tradition", which confuses me somewhat, as Bön is a survival from the pre-Buddhist times in Tibet.
Anyway, this is a fascinating little book ... it does, however, read very much like the last one in that there are a lot of things being "defined" in terms that are themselves technical and don't necessarily make things clear for the "outsider" reading it! Maybe some day I'll find a nice over-view book of the history (and survival) of Bön to get me up to speed with the subject. As noted, I was unable to find any source for this, so if you have a hankering for a copy, you're pretty much out of luck, although there do seem to be some decent basic web pages (http://bonpo.net/, http://www.bonfoundation.org/, etc.) with good info if you're interested in checking it out.