That's interesting, I absolutely hate PDF. Lack of metadata for collecting, format is difficult to support, doesn't layout well on mobile, and very limited customization (like dark mode, changing text size, etc).

Only benefit is browsers have built-in support for the format.

One thing I like about PDF is the annotations (notes & highlights) are embedded in the PDF itself. That is not the case for EPUB files, each EPUB reader stores annotations in its own proprietary format.

> Lack of metadata for collecting

PDFs have pretty excellent support for metadata. If the collection software doesn't support at least Dublin Core, that may be kind of their own fault...