I've said it before and I'll say it again. I love reading about epidemics and pandemics. I don't care if Kansas Dad thinks I'm weird. (I like to point out the books I read sell a lot more on Amazon than the ones he likes.)
Anyway, I finally got around to reading The Devil's Flu by Pete Davis. It took a while to make it to the top of my list (published in 2000). In general, I'd recommend Gina Kolata's book more. The version of Flu I have was published in 1999, but there's a new version that came out in 2001. It might even cover what was missing in the original. (I linked to the new one.) I liked her style better. I agree with both of them, though, that influenza is a great threat in our times and not given enough resources or respect.
I won't say any more because I'm about to start reading The Great Influenza by John Barry. Hopefully it'll have even more information, being published in 2005.