Hello! I recently built the Pressbooks → Grav Helios Open Reader Converter, a standalone, open-source PHP tool that turns a Pressbooks book’s XHTML export into Markdown for Grav Helios Open Reader, or for other similar Markdown publishing tools. I’m also the author of Open Reader itself, a web-first, open-source reading platform built on Grav CMS – flat-file, no database – and have always looked at Pressbooks as the leading model for open textbooks.
Just this past weekend a Standard Markdown output option was also added, using plain Markdown and GitHub-style alert blocks instead of Helios-specific shortcodes – so converted content also works in plain Grav, GitHub-rendered pages, Docsify, Docsify-This, Jekyll, and Hugo, not just Open Reader.
Example: Principles of Social Psychology – original / converted. Thanks to Dr. Rajiv Jhangiani and Dr. Hammond Tarry for sharing their work in the open!
Full details (features, licensing, how it works) are on the converter page:
I hope this is a useful option for people working with Pressbooks content! Feedback and more real-world test files welcome, especially OER books.