I really had a hard time with this poll. Even though some of WotC books are better than others, I really have a hard time deciding which one is the worst. After all, to me even the "worst" official 3e book is still better than 90% of all 3rd party d20 stuff.
I really liked the ELH. Complaints about "munchkin's paradise" are just personal opinions. I think the epic level rules work fairly well, with a few exceptions. The only thing that I really didn't like about the book was the silly epic setting found in the back of the book. I run epic campaigns where epic characters are legendary heroes and men of renown, not ordinary police men in some city where every one else have 20+ levels.
Dieties and Demigods was fairly good in my opinion. I am one of the few people who likes the "deity monster manual" idea. I like to run epic campaigns where heroes can challenge the gods, like in so many fantasy stories and legends. My complaint comes in that it seemed incomplete. I was expecting the Japanese, Chinese, and Babylonian Pantheons. I'm still waiting for a web enhancement.
I guess my vote for the worst 3e book would have to go to Monte's BoVD. (Sorry Monte!) It's stuck in some weird middle ground that's not vile, or dark enough for fans of hard core vileness, but it's too vile for more conservative minded players. The big problem, IMHO, comes from a lot of the PrCs and feats. I always expected evil to give some great benefit at a terrible cost. From what I've seen, most of the PrCs and feats, seem almost underpowered. I can't imagine any villian taking anything from the book.
Of course the worst 3e product is 3.5e. Wizards making us shell out another $90 for the same books with some minor changes.
