Also I'm interested to purchase it.
https://www.reddit.com/r/freebsd/comments/2gozvc/the_design_and_implementation_of_the_freebsd/
I'm interested in that book myself, so I took a gander at the book in the local bookstore this weekend. In the time allotment that you're allowed before the clerks give you the evil eye, I picked up a few things, including that about thirty percent of the book is never-before published material, updated to include not just the original 4.x but now 5.x thru 11.x FreeBSD. It looks good. Kinda pricey, but you're probably not "official" until you have this one.