You should install an eBook reader like MegaReader; if you run your own Calibre server, it does a good job of reading books.

Realistically, there’s not going to be much you can do with an iPad 1.

An iPad 2, on the other hand, is still a very functional jailbroken device. SNES and older emulators work great, it can play streaming videos, works with various ePub and PDF readers, and handle email and site-specific web browsing (including Lemmy).