Yep, I'm currently reading my EPUBs and PDFs on an ancient iPad 3. I researched a newer solution and settled on a Kobo Aura One (or perhaps the Forma which came out only recently) running the open-source KOReader [0], which is apparently much better than the built-in app on the Kobos. But I'm too cheap to upgrade while the iPad still works.

[0] http://koreader.rocks