I use a nook for reading novels, but can't imagine using it for a textbook. Apart from the fact the page is too small, it just takes too long to flip back and forth looking for something, and that's the primary mode in which people use textbooks. Besides, I still have my undergraduate textbooks from ten years ago on my shelf and occasionally look something up. If they'd been in an electronic format I'm sure it would…
About page size... I wondered when the iPad first came out about the screen size vs paper textbooks. I thought it would be too small given my memories of carrying all those big, painfully heavy books around. But I wanted to check my intuitions against some facts. And I happily remembered that I have an old _An Introductory Course in College Physics_ from 1958 on the shelf. The pages from 1958 measure 5 1/4" by 8 1/4"…
Physics textbooks rapidly get smaller and lighter the more advanced the material gets, though.