I think I've bought most of the non-fly books in print (and a few of the fly books, too). I agree that the best overall book is Bill Herzog's 'Color Guide to Drift Fishing'

For my second choice (hey, it's Christmas!) I STRONGLY recommend Trey Combs' 'Steelhead Fly Fishing' even if you're a gear guy (like me). In paperback it costs $23 via Amazon and is the best bargain in fishing as it's a large format 500 page book. Combs writes beautifully and there is no way you could read this book (skipping the parts on assembling shooting heads and the like) and not end up a much better fisherman given his analysis of the fish, holding water, presentations, etc. Along the way, you learn about the great steelhead rivers and some of the nutcases who spend their lives fishing them. It's a must-have book.

Third pick is Jed Davis' 'Spinner Fishing for Steelhead, Salmon and Trout'. This is an excellent all round book (even if you don't fish spinners) as it talks in detail about water temperature and color, size of lures and likely steelhead behavior. Changes the way you fish, for the better.

If you're some sort of reading demon another OK book but lacking the focus and detail of the previous three is Jim Bedford's 'Steelhead Saavy'. However, the advantage of Jim Bedford's book is that it addresses every technique -- drift fishing, float fishing, spinners, plugs -- though not in as much detail (and it's aimed at anglers fishing in Great Lakes-type rivers).

I've also got a bunch of specialty books on jigs, plugs, etc, and particularly recommend Dave Vedder's Float Fishing for Steelhead (though to be honest I've yet to really put his advice to work, but his instructions and descriptions are very clear).

I bought all of these through Amazon.