Try Overdrive app for iPad, iPhone and Kindle. You can download free ebooks and audiobooks from your local library. Kind of complicated to use at first, but once you get it figured out, great app! You'll have to register through Adobe (just an email address) for access to some books.
You can download the audio book from dailybooth.com/buyebook/22146761 or thepiratebay.se/torrent/3326896/. You can also check your local library and see if they offer audio books. When you sign up with www.book-club-offers.com/audible-gold-free/, you get a free audio book; you can pick To kill a Mockingbird.