Go read The case against textbooks. In that post, the author makes a number of assertions about textbooks, some of which I disagree with:

You can’t annotate it.

I don’t know about other students, but I tend to scribble all over mine. Certainly you can’t share your annotations with another student’s, but you can write up your own in the margins, over the text, anywhere!

You can’t search it.

That’s why publishers create a detailed index–it’s even better than searching it, since relevancy is defined by the book’s creators.

You can’t access it if it’s not in your posession.

I agree…but I think the point is invalid. You can’t access anything if it’s not in your possession. If you don’t have “possession” of a network resource, you can’t access it either.

You can’t copy out important information and paste it with other important information.

A lot of people forget that the terms “copy/paste” come from text, before the digital age. Yes, you can literally clip out a portion of your text and paste it somewhere else…

You can’t share it in any meaningful way.

Well, you can lend it to someone. Is that meaningful?

Anyway, the article is pretty cool, and the main point–which is that an interactive, online medium is better for textbooks than paper–is good.