Don't forget Steve Raymond, Steelhead Country. Bob Schmelzle of Seattle recommended it and I could really relate to his perspective and style.
Bates' book on Atlantic Salmon is a classic, even though it's a salar book the section on Bates collaboration with Syd Glasso makes it special and the patterns are gorgeous and influence the steelhead tyer.
For Great lakes fishing done right you can't beat the Kustich Bros book "Fly Fishing For Great Lakes Steelhead", a classic focusing on practical success without succumbing to the split shot / drift methods disguised as fly gear.
I second the Combs book, and my old "Dry Line Steelhead" by McMillan sits on my desk along with the other most influentials.
Thanks to a very good friend Fine and Far Off by Jock Scott is the first book on this shelf of top reads. Again a salmon book but very influential in both casting and fishing technique.
IFFF Certified THCI @ 2005
Capeflyfisher Guide Service
Island Hopper, Guitarist, Incurable Dreamer
and Founder, Worldwide Flyfishing Forum