The great granddaddy of them all is "The Ashley Book of Knots" by Clifford W. Ashley. I have a copy and think anyone who seriously uses knots should at easy have easy access to a copy.

That said it is not necessarily the handiest book to learn knots from. Terminology is variable, knots, even quite familiar ones, are hard to look up because the names and designations are confusing. It is also fairly expensive at $65 list price. But it is considered to be the bible of knots and is considered a standard reference on the subject.

It is also a fun book to work your way through. I just nibble at it piecemeal but a friend spent a year's worth of late evenings and free time working his way through every knot and piece. He picked up a lot of hands-on experience and know-how. There are far worse ways of spending one's spare time.

The thing about knots is that pretty much everything anyone needs to do can be accomplished with far fewer than Ashley's 3900 knots. Most people on the street only know two or three. One of which is likely a false knot that just might get them killed if used in a critical situation.

But even professional sailors and mountaineers might only use six or seven knots regularly. Learn a half-dozen basic knots and learn to make them well and you have all you really need. Unless you just like learning new knots there isn't much need for a book.