(Disclosure: Manning author twice, Leanpub co-founder.)
Now, at Leanpub we're going to be rolling out our own courses in the next couple months, so we agree with O'Reilly that there are lots of great ways to produce and distribute learning material. However, the book is the best, most general and timeless way. We're committed to selling DRM-free ebooks in PDF, EPUB and MOBI directly from on our own site for the long term.
The ebook world should not just give up and sell everything through Amazon. I like Amazon--they do a great job of focusing on customers, I have Amazon Prime, and I'm really happy that Jeff Bezos is a good owner for the Washington Post. But we should not let Amazon become the only seller of ebooks.
Stay tuned for something else we're planning in this regard in a few weeks...