The forth book from the novel adaptation of the Hilda series is Christmas centered despite the book's title not mentioning it. It covers the first half of the Season 2 using the Yule Lads as a continuous plot point between self contained adventures with the Gryla confrontation and the Sonstansil blooming. So pretty solid reading for the Christmas season, specially since you don't see these fuckers quite often on media in general (or any interpretation of other Christmas folklore in general besides what americans are familiar with). It also doubles as alternative history since the setting is Scandinavia without Christian elements, only pagan and coming to a festivity quite similar to Christmas giving away presents and decorating trees.
>post some books about how the guy learns Christmas was good after everything he went through
The common theme of Hilda media (comics, Netflix series and novels) is that things are not often what they look like, which this book follows, the Yule lads are corny and a little obnoxious but they don't seem malicious until they start kidnapping children and after that Hilda realizes they are doing it because they are basically are Gryla slaves. But in this book in specific the moral is "use your fucking brain, retard", the Yule lads have been hunting children for literal centuries and never crossed to their minds try tricking Gryla by giving her literally anything but children as food until Hilda crossed their path and suggested it.
So this book is quite unique in that regard too, sine it's Christmas related and it's not about "learning the true meaning of Christamas", "help Santa to deliver the presents" or something corny like that, but about the child kidnapper goblins learning how to try Gryla into not killing children.