The Sonnets by William Shakespeare, $13.99 --> $3.99
This deal won't appeal to everyone, but if you're an English literature student, or a fan of Shakespeare, this app features 154 professional video performances of Shakespeare's sonnets. It's huge -- almost 1.5 GB! But totally worth it, imho.
The Verge covered this when it first came out, and the publisher's website is extremely informative, featuring links to all the performances.
This app is by the same guys who did the Barefoot World Atlas, currently featured as one of Apple's 5th anniversary freebies. And yes, this one is iPad only, sorry!
Last edited by dclose; 07-12-2013 at 09:41 PM. Reason: Confirmed that it's available only for the iPad.