Here are some links where you can purchase (not from me) some of the more popular still in print books.
I have all of them. They're definitely worth the investment if you're into classic flies in any way, shape or form.
The Blacker Compendium - Bob Frandsen, Dale Darling
Classic Salmon Fly Patterns - Michael Radencich
Tying the Classic Salmon Fly - Michael Radencich
Carrie Stevens: Maker of Rangeley Favorite Trout and Salmon Flies - Hilyard and Hilyard
Tying Classic Freshwater Streamers - David Klausmeyer
Thunder Creek Flies: Tying and fishing the classic baitfish imitations - Keith Fulsher and David Klausmeyer
Below are links to some of the most popular, out of print, classic salmon fly books available.
These books are library archives available for download.
William Blacker - The Art of Fly Making (1842)
William Blacker - The Art of Fly Making (1853)
Ephemera (Fitzgibbon) - The Book Of the Salmon
Ephemera (Fitzgibbon) - A Handbook of angling
Francis Francis - A book on Angling
J.H. Hale - How to Tie Salmon Flies
J.J. Hardy - Salmon Fishing
George Kelson - Tips
George Kelson - The Salmon Fly
A.E. Knox - Autumns On The Spey
T.E. Pryce-Tannatt - How to Dress Salmon Flies
Frederic Tolfrey - Jones Guide to Norway
Major John Traherne - The Habits of the Salmon (Traherne's Flies arent actually in this book, they were published in The Fishing Gazette).
Sir Herbert Maxwell - Fishing at Home and Abroad
Sir Herbert Maxwell - Salmon and Sea Trout
Fraser Sandeman - By Hook and By Crook
Fraser Sandeman - Angling Travels In Norway
Alexander Mackintosh - The Driftfield Angler
David Foster - The Scientific Angler
Thomas Tod Stoddard - The Art Of Angling As Practiced In Scotland
Hewitt Wheatley - The Rod and Line
William Peard - A Year of Liberty
W. Earl Hodgson - Salmon Fishing
P.D. Malloch - Life-history and Habits of the Salmon
William Scrope - Days and nights of Salmon fishing
Ogden - Ogden on fly tying
Hi-Regan - How and Where to Fish in Ireland
Henry Wade - Halcyon
H. Cholomondeley Pennell - Badminton Library - Fishing - Salmon and Trout
Trout, Bass/Lake and Salmon Flies
Mary Orvis Marbury - Favorite Flies and their Histories