Short answer: these books are the only ones of their kind and
although they don't cover MSAR in great depth they are valuable
as a starting point and a common frame of reference. If your
group has members who are not yet on the Internet, a print book
is a must.
There has been discussion of the books in the Usenet newsgroup
rec.equestrian. See the Usenet archives on groups.google.com.
Una Smith
Santa Fe County Sheriff's Posse, in New Mexico
(No, we haven't been called out either to search for pieces of
the space shuttle, but the debris field is way over in eastern
Texas, a good 15 hours drive away.)