Alder's Grove

I am beginning to notice a trend, in the few books I have read where there is a woman In Charge, On Top - where that's the whole concept of the novel - where she decides like 3/4 of the way through the story that she wants to be on bottom, or he decides he wants her to submit and she goes along. And all of a sudden she's all submissive and ... I signed on to read an Fdomme story.

Is this common, or just the stuff I've read?