Bruce Byfield has written Designing ebooks with free software, which teaches several methods that help you to gain control over the creation of your ebooks. All it takes is two open-source tools that are free to download: LibreOffice and Calibre, plus some trial and error to get the precision and professionalism you want.
Designing ebooks is available as a free download in PDF, EPUB, MOBI, and ODT versions, as well as a low-priced print edition. Links to all versions are on the book’s website.
Designing ebooks is a companion volume to Bruce’s 2016 book, Designing with LibreOffice.