The very notion of A/B testing a piece of art disturbs me profoundly. The idea that publishers would say, "Our analytics show readers engage with these types of passages so you need to increase your usage of X passages by 50% and use 50% more words from this list", paints a fairly dim view of the future of artistic expression in a world that is concerned with profitability over substance at an increasing rate.
Publishers already have a far heavier hand than I'd like them to or most people know about. Giving middle manager types data when it comes to artwork can only lead to place where self expression through authorship becomes a dead art-form.