Barr Flies: How to Tie and Fish the Copper John, the Barr Emerger, and Dozens of Other Patterns, Variations, and Rigs by John S. Barr and Charlie CPrime Fly Company
Barr Flies by John Barr and Charlie Craven should be a foundation fly tying book in everyone's library. These are two of the greatest modern tyers around, and their innovations and named patterns reach the dozens. Need reassurance? John Barr created the venerable Copper John, arguably the world's best selling fly. I rest my case.