[paipa]

I'm convinced there is no new typesetting engine whatsoever.

Amazon simply re-processed some of their books, added soft-hyphens, replaced certain letter pairs with unicode ligature symbols and that's it. Even kerning must be hard-coded into them somehow because side-loaded books, regardless of format (AZW3 or MOBI) don't show any signs of kerning with Bookerly. No, the o is not tucked under Y in "You". Maybe it is for some Amazon books, but not for side-loaded documents. Same ugly letter spacing as it has always been.

So the mysterious "typesetting engine" isn't on the device itself. It's a phantasm, it doesn't exist. All of it is done on Amazon's side, and you can get it for some books you've bought.

Having said that, at least someone can make a Ligaturize plugin for Calibre now, replacing letter pairs with Unicode ligature symbols, as your Kindle at least finally has a concept of them now and will display them. I just tried it out and it works. So if you're willing to mess around with plugins like Hyphenate This and a yet-to-be-written ligaturizer, kerning will remain the only thing that your sideloaded books won't have. Which is, honestly, still baffling to me given how trivial it is, but we'll survive.

Bottom line is, Amazon didn't do crap. A bunch of interns ran some scripts on a couple of thousand books. That's their new typesetting engine for you.