Here are some of my favorites that I have not seen listed yet on this forum, all available at Amazon:
The The Il Fornaio Baking Book  (1991) - yes it may be a bit informal and not too detailed, but I made some great bread from this book long before I knew what "artisan breads" were. Beautiful photographs too.
The Tassajara Bread Book  (1970, rev 1995) - great for beginners and a pleasure to read, a sentimental favorite of mine as my Dad used it when I was a child.
I see Dan Leader's Bread Alone  Bread Book is advertised on this site so I won't bother mentioning that one other than to say it has a lot of good recipes and good discussion of flours, although I find his emphasis on temperature to be too rigorous and impractical for the home baker, preferring Reinhart's methods in BBA instead.
I think I did see Maggie Glezer's Artisan Baking  book (2005) mentioned somehwere here but I'll mention it again as it had some recipes I tried that came out very well, not to mention a lot of intersting annedotal chapters on various artisan bakers, millers, and such.