As long as you brought up e-readers, some time ago I bought a CD of copyright free e-books. I downloaded a free program called Calibre and used it to convert the text into ePub format for our e-readers.
We now carry over 1,500 ebooks (all on one CD) aboard. There are NOT primary reading books, but when we just don't feel like reading any of the paperbacks, or have gone through the supply aboard, we ALWAYS have something to read.
You would be surprised how enjoyable some of the old classics can be!