This guy is actually a really good professor, I'm familiar with some of his other stuff and he's definitely legit. My girlfriend had his videos (thinkwell) for her class a couple years ago, I thought they were good.
He also wrote a book called heart of mathematics which is pretty interesting...
I'd always choose paper, but if its a technical book, as useful as a search is, the ability to scribble in notes etc.. is far more useful to me. The free part of e-books is what makes them good, not the reading on a screen.
I buy books to the point of it almost being a problem. I've never had a significant problem with amazon (~200 buys) except for my Diff eq by Arnol'd, two pages were stuck together at the bottom (no loss of text though). I have many cheap(<$20) textbooks that are just fine.