Most of the eBooks you download from the AppStore are actually applications
containing eBooks along with an eBook reader, and you sync those in the same way as any other App downloaded from the AppStore.
If you have an eBook Reader that allows you to download and add extra eBooks then refer to the instructions of that eBook Reader on how to add them.
Yes, AirSharing allows you to mount the iPod on the desktop as a wireless drive. Search the AppStore for it and read about it there, or here:
http://www.avatron.com/products/