You have to experiment.
I plan on changing alot of my covers.
And I plan on working on all my front matter and back matter.
Additionally, I am playing with prices. January 3rd is just as good as January 1st to start tracking numbers.
So, my short point is: experimenting is important. I played with unusual covers at the beginning of the year when I saw some title called 50 Shades of something climbing the erotica charts. Ya that one. It proved you didn't need a naked body on a book to sell. And now the trend seems to be heading towards less skin.
I am going to play with my covers and see where it takes me.
I am going to play with prices and see where it takes me.
But I won't play much with what turns me on. You gotta write what you love. For sure I am sticking to that...for now. :)