Well put–re the variants (which can naturally arise from various ways of “re-weaving”
the Fig.8. One concern about these knots is ring-loading insecurity–i.e., were the
eye to be pulled open as though the knot was a bend joining its ends. Another concern
might be with imbalanced loading, if the end-side eye leg can somehow be loaded
in isolation or strong bias, it might pull out (it’s like the Thief knot, then).
As for the cost of [i]ABOK, Amazon now says “38 Used & new from $29.99”,
and lists their own at $50. (I’ve bought a book from the A. Marketplace for 1 cent
(plust $3.99 shipping)–in fine condition.)