Originally Posted by Pat Thompson
Brown, Son and Fergusson, in Glasgow sell a couple, "Knots Splices and Fancy Work" and "The Harrison Book of Knots". Have a look HERE
I have both of them and found them very useful.
Another vote for the Harrison book of Knots. It's more "user friendly" than the Ashley BOK (and cheaper!) and while there are plenty of other books on tying knots Harrison seems to aim in particular at the creation of bellropes.