If you have a laptop with a wireless card handy, you can
make an ad-hoc network and connect to that.
Alternatively, you could upload your books to a website such as box.net, go to your local library, and then use stanza to download them by selecting "Get books", "edit", and then "Add book source".
If neither of these work, you're out of luck. There's currently no other way *on the iPhone* to get books into Stanza.
This will be changing in iPhone OS 4.0, where there is a shared folder that apps will be able to access, as well as your computer.