From the Colossal article about this melding of audio and print:

The system uses patented computer vision and other modes through a smartphone or smart glasses to track your place in the book and play the corresponding audio. Whether music, ambient sound, or narration, the soundtrack moves with you at your own pace.

While I think there’s lots to explore in the intersection of books and sound, this feels like a bit of a Juicero situation. I’m not sure there’s anything here that couldn’t be accomplished just by a playlist set to ‘repeat track’, with the reader pressing ‘next’ when they turn the page.

More info here if you’re interested: https://www.radioposter.com/blogs/paper-fi-blog/paper-fi