I just took a closer look at a book that I'm 'stalking,' because it's in my local book store as well as on Amazon.
I like to check the rank in my book store, which places its books in best selling order.
A week ago this book was at no. 2 in the book store, at full price, but it's now lost that place and is half price.
When I look at the info. on Amazon it reveals that it was first published in October 2016, so the author has got five Christmas markets out of it.
It has sold, or potentially sold, I haven't checked, prior to: Christmas 2016, 2017, 2018,2019, 2020, and 2021.
There is of course the possibility that it only sells during the period before Christmas, and not at any other time.
It's full price on Amazon, by the way.
It seems that a Christmas story has pretty long legs, it will sell and keep selling as long as there's Christmas.