I also love Trout Bum, even though I'm not fond of most of the other books by John Gierach. But one of my recent favorites is A Fly Fisherman's Blue Ridge by Christopher Camuto. His writing is absolutely fabulous.
A recent publication that I also really like is Trout Hunter by Rene Harrop. It is not really a how-to, and not really a muse, but it has some great information and some great writing. If you have fished the Henry's Fork it will have a special meaning to you.