Convert HTM to EPUB

EPUB ebooks can be created from pretty much any document or text source and HTML files, or documents structured in HTML are one of these sources. Many word processors actually offer export to HTML, so texts in this format are not that rare. The easiest way how to create ePUB ebook from HTML source (which is what htm to epub conversion pretty much is), would be to use some dedicated ePUB software or ebook management tool. Many page layout tools (InDesign, Publisher etc.) also usually offer support for EPUB format.