Safari on iOS does client-side storage, you could let someone read a stored book offline. It would make pirating them a little easier though. Not much easier be

Safari on iOS does client-side storage, you could let someone read a stored book offline. It would make pirating them a little easier though. Not much easier because it's not exactly hard now, Calibre has a plugin that imports them and breaks the DRM. Heh, we could buy books from Amazon, de-DRM them, and read them in iBooks. It's probably the best reader software for the iPad other than Kindle.