Find someone who does it and spend an hour watching them. You'll learn far more than you can reading a book for ten times as long.
Try local fly shops, sportspersons meetings, or TU meetings. If you can't find a human, you may be able to watch online videos if you can get past gross fingernails, mouth breeders, and the other assorted undesirable elements of people who are trying to (poorly) market their "skill." At least it shows you basic things. The movements are more important than the static pictures in a book.
Failing that, the library is a better start. You'll soon realize that every fly tying book ever written likely re-hashes the same course of learning; most of those books exist for the pattern listings at the back. The Interweb will fulfill that role nicely, too.