https://www.literatureandlatte.com/scrivener/overview
Pressbooks is our favourite platform. It's user-friendly, has lots of features, and will be useful to most people who want to create eBooks. Highly recommended!
http://www.apple.com/ibooks-author/
Although beautifully designed and capable of producing stunning eBooks, the app isn't particularly useful in many contexts because it's limited to Apple devices. Sorry, Kobo owners. :-(
If you'd like to convert files into an eBook-friendly format, use one of the following free online tools:
These sites offer no frills eBook-making. You take a PDF or a MS Words file and convert it to an eBook format. No design options are available.
Once you've created or downloaded eBooks, you'll need to manage them.