Since being published, my book, Last of the Glow Worms: Memoir of a Nuclear Weapons Technician at the End of the Cold War has fluctuated in rankings on Amazon. The recent events in North Korea have brought the threat of nuclear once again into the minds of Americans, just as it had during the Cold War. I saw a spike in the book rankings a few days ago, when North Korea launched their most advanced missile system to date.
I have learned that news and popular sentiment do have an effect on what people are reading. Holidays are also a good time for book sales. If you are an author, try to schedule your sales promotions and KDP giveaways (if on Amazon) around the holidays. I found out this marketing strategy worked when I published my first book, When Giants Speak in 2011. I had 400 downloads in a day, and every page read does count towards your money earned with the KDP worldwide fund.