Can't get much better for cross device than html. Pdfs are useless on most devices, especially kindles and phones, since text doesn't reflow when you zoom. As

Can't get much better for cross device than html. Pdfs are useless on most devices, especially kindles and phones, since text doesn't reflow when you zoom. As to anti-piracy, I don't know what to tell you. The hardest format to pirate would be a physical book. Ebooks, pdfs and videos are all easy enough to redistribute without really good drm.