Ebooks are phenomenal. Mostly because you can bring a lot of them where ever you go without being burdened with the weight of a lot of paper. I know – the feeling of sitting with a real book is irreplaceable. But so is the fatigue from a way too heavy backpack.
In my link collection I have put references to a couple of my favorite tools in terms of libraries and software packages for managing downloaded books. Go check them out.
https://www.gutenberg.org/Gutenberg.org – online library with thousands of public domain books. 
https://calibre-ebook.com/Calibre – the ultimate ebook manager for all current computer systems