[ghero]

I think a good feature for this kind of e reader will be something like "term discovery".
In order to build this feature, first the e reader needs access to a bank of digital scientific journals, papers, publications, and trusted online scientific info resources. And when user selects a term on a paper that he is reading, he can use "term discovery" to get a list of scientific materials that discusses topics relating to that term, which he can either view/pre-view or purchase those materials. Also with such bank of materials avaliable, another feature would be to have AI that reads the bibliography, and automatically fetch cited materials from the scientific material bank or online, and compile a list of fetched materials, so the reader can view or purchase them.

Another attractive feature would be to allow scholars/professors (especially those who are famous and widely respected in their fields) to constantly publish their researches on the digital book store used by this kind of device. And allows a social network style system to let readers to follow them and subscribe their works, maybe even discuss them. (I guess another related feature would be to search publications/papers by author in the digital book store.)