Here's a few more for you Steve. The first is a bit outdated but it's the book I learnt to tie from and still has very relevant info...
Fly Dressers Guide. By John Veniard.
The second I bought on a whim and it's pretty good although mainly instructional in technique which you might find elsewhere. Definitely worth a read though as there's some bits you wont find anywhere else...
Tying flies in the Irish Style. By E.J. Malone.
This one is one of my favourites just because it's got a mind boggling array of dressings. Some old, some new but they're all just added inspiration...
Irish Trout and Salmon Flies. By E.J. Malone.
This last one is the mother of all technique books and quite honestly not something to read from cover to cover. It's definitely a case of dip in when you're in a quandary about how to get things to work...
Fly Tyers Benchside Reference. By Ted Leeson & Jim Schollmeyer.
Another one definitely worth a read, several times...