: Apply unique CSS to ensure your "book" version looks better on e-readers than a standard print-to-PDF. Top Libraries for the Job
: While primarily a world-class reader for displaying EPUBs in a browser, it is the industry standard for interacting with eBook data via JavaScript. The 3-Step Conversion Workflow RSCE JS epub
: Script the conversion of hundreds of posts in seconds. : Apply unique CSS to ensure your "book"
You don't have to build a ZIP archiver from scratch. Several high-quality libraries handle the heavy lifting: RSCE JS epub
If you're not looking to write a custom script today, there are excellent existing tools to bridge the gap: Generating an EPUB File in the Browser - Jim Nielsen's Blog
: Let users "download as eBook" without needing a backend.