I mean that I've chosen my first paperback to start tomorrow and, when I finish it, I'll then look at that day's theme and see if I have a suitable book to fit that day's theme, or maybe the following day's if I'm not ready to start another one immediately.
Similarly, I'm going to read the Kindle novel I've picked up that fits November's theme for as long as it lasts and then see what on the Kindle fits the theme of that day when I get there!
Could be complicated . . . . .