We use CSS paged media to create e-books and invoices (using weasyprint [0]). One of the most helpful resources for me was print-css.rocks [1], they cover a lot of what’s possible and include which tools support which parts of it (tools targeting paged media, browser support is essentially non-existent and outside using JS to fake it with paged.js, not relevant). The expensive tools tend to support more features, but thanks to some donations/sponsorships, weasyprint has really caught up and now supports a very large part of the spec.

> Especially in combination with headless browser pdf generation

I have no idea why you’d want to do that. Browsers are bad at it, dedicated tools are great at it.

[0]: https://weasyprint.org/

[1]: https://print-css.rocks/

[2]: https://pagedjs.org/