If you were happy with eReader on your Palm, you might as well stick with it on the PPC. The eReader site offers a free PPC download -
http://www.ereader.com/product/browse/software
I placed all my eReader books on my SD card. My installation of eReader installed a folder called 'Peanut Press' (precursor to eReader and even PalmReader) in the My Docs folder I have there. I installed the books via My Computer > Mobile Device > My Pocket PC > SD Card > My Douments > Peanut Press and simply dragging/copy them over.
There are many excellent readers out there and everyone has a favorite. Use whatever you like. And don't forget sites like
www.memoware.com for freebie books that can be read on just about every reader. eReader books are still listed as PalmReader there, BTW.