I disagree!
For learning knots for Cub Scouts I recommend “Knots and how to tie them” by Boy Scouts of America.  It is a white booklet with 31 pages and covers all the Boy Scout required knots and then some.  I think is cost about $5.00 at the Boy Scout Store.  It is a waste of time, money, and effort to study the large knot books.  If you are into mountain climbing or sailing that is a different issue.   
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