I'm very guilty of skimming before diving in to longer posts. Therefore, I find I'm more likely to engage intellectually with something that contains a premeditated structure and is well written. I usually make a judgement in less than 20 seconds. To your point, well-articulated and thought provoking posts are more likely to grab my attention.

Sn Ebooks is interesting but when it comes to books in general I'll probably not invest my time into something until I've convinced myself that it's worth it. My belief is that most adults are very pragmatic when they have to invest intellectual effort, such as a book requires, or try to learn something new. For fiction I think they want to know something has cultural value (maybe via a book review or reccomendation) or that it will provide a good deal of enjoyment while reading. For non fiction, they want to feel they are learning something that is immediately relevant. All of this is just to say, I would gladly opt into reading an ebook on SN if it satisfies these checks and I think adults generally operate similarly.