[kelnos]

Back in 2009/2010 I worked for a startup that was doing something like that. The screens were a bit bigger (maybe 10" or 12"? can't remember), and they were LCDs, not e-ink. The device was heavy, but the intended market was college students who could read textbooks on it, and take notes directly on the book's pages with a stylus. (It also had a web browser and dedicated note-taking app, among other things.)

The product's timing was off; the first iPad came out while we were still building it, which made it quite a bit less attractive, and it likely could be made much thinner and lighter today. (What really killed it was the founders' inability to secure digital rights from any textbook publishers... though arguably it would still have been a tough product to sell even without that obstacle.)