This plugin configures AkashaCMS/AkashaRender to produce XHTML files corresponding to EPUB3 specifications. With it, one can produce a directory structure that can be bundled to create an EPUB. A companion tool, the EPUBTools project, is a tool for bundling EPUB files. The two are designed to work together.
For documentation see: https://akashacms.com/plugins/akasharender-epub/index.html