I'm doing a Christmas sale on two of my Christmas romances for the entire month of December and it's going very well. I'm wide so I don't use countdown deals, etc. I just discount and advertise. In romance, holiday-theme books do very, very well from Thanksgiving to as long as February. Those readers eat up Christmas books. I write in several genres so I refrain from releasing anything new during this time and either I will write a Christmas romance or do what I did this year and just do a sale for existing books. It could depend on genre, etc. Not sure how book sales do overall in other genres this time of year but they do extremely well for romances if the book is about Christmas. Romance readers LOVE the Christmas books. They eat them up.
For me, it's safer not to release anything that's not holiday-themed this time of year and just wait till next year to release the other stuff.
A lot of authors do box sets during this time of year though. I'd suggest doing a discount set of a series and you might sell well during this time.