[throwaway290]

If you made a durable copy of a book in your example to keep for yourself and use later that's already a grey area. But no one does it with books. People do it with other media tho, and big surprise get prosecuted for it. As you may know, in developed countries people get served notices for torrenting

But if you make books contents available online via some service that regurgitates its contents you would be totally sus because you can be considered in a business of selling derivative works.