I’m a contributor – I did Kafka’s The Castle , Agatha Christie’s Giant’s Bread , and Stella Benson’s The Faraway Bride for this launch – and I’m happy to answer any questions about Standard Ebooks.
What kind of features does "advanced epub" provide that "compatible epub" cannot?
1. renders the cover as a JPG from the native SVG
2. converts more complicated selectors (e.g. :nth-of-type, :empty, etc.) to classes and class selectors
3. renders MathML as images
4. renders SVGs as images
…and a bunch more things to make it work better with older ereaders, which tend hang around for a long time.
It’s worth pointing out that the Kobo builds are closer to the “advanced” build as they have great native support for MathML and SVG. But the build step adds in a bunch of Kobo-specific markup to make it work better there.
In my experience, Apple Books does the best with the advanced builds, but it doesn’t support SVG covers so you end up with autogenerated ones, which seems a shame. I’ve sent a couple of feedback issues to them over the years, but if anyone else wants to also do this feel free.