I've managed a few titles that had feature ads in the week before and after Christmas. It's like any other ad time, so it can be amazingly good or kinda (comparatively) meh. We had a title one year hang in the overall Top 100 for 2 months after its 99 cent BB Christmas-time feature. Year before last, on Dec 28, we had weirdly lackluster immediate sell-through (again, comparatively speaking -- it was still
good sell-through) for a freebie whose series had seen gangbuster sales during every other promo before or after. Those were the extremes from the probably 10 or so titles we ran at Christmas-time as BB features over the years. Everything else fell in as about par with the average against other times of the year. That's over...hmm, I never counted the exact number of BB feature ads I managed, but it was probably around 100.
Specifically for a Christmas novel, we had one that ran as a BB feature, but it ran in late November. It was PNR/Contemporary Romance, plus it had an exclusive bonus short story by Debbie Macomber in her popular 'Shirley, Goodness and Mercy' series, so not a good compare with most indie Christmas titles.