I'm glad you're already getting Gonzo's book. It's worth it.
The other recent tying book I consider
really indispensable is Kelly Galloup's "Cripples and Spinners." The "Galloup's Cripple" style is quickly becoming my favorite all-around fly, and the "Ellis Triple Wing" is another favorite spinner imitation.
Another good angling entomology book I forgot to mention because I haven't read the whole thing is Aquatic Entomology by W.P. McCafferty, a leading mayfly entomologist. It has better coverage of the insect orders outside the "big three" than any other book I've seen for anglers, at the expense of relatively little detail about individual mayfly or caddisfly species. I don't own a copy, but I really should. I have it in front of me right now, checked out from the library, and it seems excellent.
I really have to go get some work done right now, but you can see the list of books and papers I (mostly) own here:
http://www.troutnut.com/fly-fishing-books