For those of you that didn't see this on slashdot.org. Dominic Giampaolo, the guy that wrote the BE OS Filesystem, wrote a book about it that has gone out of print. Since the book has gone out of print the author is now making a electronic version(in PDF) availible on his website. http://www.nobius.org/~dbg/
For now he had to take the book offline because of too much traffic but someone is currently mirroring his website at http://biggestpos.com/pfs/
-Chase