I simply don't have the time to make an in-depth study to entomology. With this book I don't feel a need to. It has chapters on the basic techniques of fishing Wets, Dries, Nymphs, which I find very helpful. But what makes this book special is that Mr. Ames devotes a full page to each stage of most northeast flies, and describes where and when those insects can be found, how they behave, and how they can be caught.
Before I head to the stream, I simply read up on the insects I expect to find and, therefore, have a solid game plan in place when I step into the water.
Also, the photography of the flies is great.
This is one of the most used fly-fishing books I own.