Now a days eBooks reader increase day by day due to digitization.
Adobe PDF Reader is most popular reader but now online reader prefer ePUB reader over PDF Reader.
PDF documents have static view means fixed document view but ePUB document is responsive means auto adjustable with user screen.
How to Create eBook with Google Docs
EPUB can be create using desktop application but you can easily create with Google Docs.
create one simple word file or write in google docs and upload it to google Drive.
As upload or created google docs download Go to File Menu and choose Download as EPUB.
As you Click your EPUB file will download and you can copy to your Tablet or Mobile to read as Ebook.
You can save it to google books websites and read it from anywhere and any time.