@aeschylus
So those were some technical pre-requisites we spent a lot of care to get right. Looking into the future of reading, we proceed mostly by phenomenology. Everyone who contributes to the reader has extremely strong and mature opinions about how their kind of reading works, and we build the primitives to support that.
As an example, a very unsupported form of reading by all current software is deep reading of non-linear content like textbooks and academic papers. The screen and software of the kindle and remarkable make it exceedingly difficult to navigate a table of contents in a fluid manner. You cannot explore and map the work in your mind, but are instead forced to peck and teleport into random parts of a book, or know ahead of time what you're looking for.
Scanning a text at multiple levels if depth is a fundamental workflow of paper reading, often called "reading in layers," and we try to keep this in mind as we evolve the software. For more on this, have a look at Mortimer Adler.