I have both Zymurgy and BYO. They are fine, but most of what I read in there I already know from this site. Of course it's always fun to get in the mailbox. Draft is nice when I can find it, but unless it's an impulse buy, I probalby wouldn't spend the extra $$ on it. Great photos in there though.
I like Randy Mosher's Tasting Beer. Good read and informative. not so much abotu brewing as just enjoying beer more. Designing Great Beers is pretty good and describes styles and shows past AHA winners recipes.
howtobrew.com and the book to go with it is my first choice for Homebrewing book. Complete Joy of Homebrewing and Homebrewing for Dummies (yes, it's actually a very good book!) are a close second.
Have not had a chance to read YEAST yet, but it's on my list. And there are a few books on more specific styles such as Belgian beers (Brew Like a Monk) and even Wheat beer, Brewing with Wheat. Probably lots more.
All the books I've ever bought have been worth the price of admission.