The Yellowstone Fly-Fishing Guide by Craig Mathews and
Clayton Molinero
Mathews and Molinero's book is another excellent guidebook
on
Yellowstone National Park fishing.
I found this guide to be very helpful on covering both the waters to
fish as well as those to pass, as being barren or poor fishing in general.
I especially enjoyed the hatch charts
and the recommended choice of fly patterns for specific waters.