"Physical textbooks lack portability, durability, accessibility, consistent quality, interactivity and searchability, and they're not environmentally friendly."
Poppycock! An e-reader, dropped once will break, unlike a book, making the durability and portability questionable. While the quality of an iPad, may be consistent, so are conventional books. As far as interactivity, a book requires you to physically manipulate a page to get more information, activating parts of your brain associated with learning. An e-reader requires you to stare at a screen that is as easy to ignore as any TV commercial. Searchability? That is called an index. If you don't know how to use one, you won't do much better with keywords. Finally, environmentally friendly? E-readers are made of non-renewable resources that must be mined, causing environmental destruction, toxic byproducts, and greenhouse gasses to power them. Books are made from trees, which unlike rare earth metals are renewable.