Trout do at least 90% of their feeding subsurface. That is a proven fact. To take advantage of this fact you must learn to fish below the surface. Dynamic Nymphing, by George Daniel is a great new book that focuses on fishing subsurface. George goes through several styles of nymphing and explains why they work and when to use each technique. Dynamic nymphing also has pictures of George's fly boxes filled with his go-to patterns.
George is one of the best anglers I know and Dynamic Nymphing promises to make the "must read" list for serious fly fishers. I plan on soaking up every last drop of info from his new book over the holidays.
Dynamic Nymphing is available through most fly shops or amazon.com if you don't have a fly shop near you.
George caught the Rainbow below while nymphing a western tailwater.