I think academic books should be free.
It's not a radically new proposal, but I'd like to clarify what I mean by "free". First, there's the financial sense: books should be free in that there should be no cost to either the author or the reader. Secondly, and perhaps more importantly, books should be free in terms of what the reader can do with them: copying, sharing, creating derivative works, and more.
I'm not going to go down the murky road of what exactly a modern academic book actually is. I'm just going to take it for granted that there is such a thing, and that it will continue to have a niche in the scholarly ecosystem of the future, even if it doesn't have the pre-eminent role it has at present in some disciplines, or even the same form and structure. (For instance, I'd be pretty keen to see an academic monograph written in Choose Your Own Adventure style.)