Book Creator makes it very simple to take a piece of writing (or pieces of writing!) and turn them into polished, easily accessible, and engaging (read: you can make them interactive with links and audio!) products.
Book Creator offers a completely free option, completely, free! You get one library with up to 40 books in it! Great to play around with before you dive into the give-me-more-space-for-more-books-it's-so-much-fun world!