I'm a huge fan of Mark Forsyth's books: The Etymologicon and The Elements of Eloquence being just two examples of his excellent writing on language. When he announced he'd be writing this small tome about the history of Christmas, I pre-ordered it, and I've been sitting on it all year, waiting for the Christmas season's approach to read it.
I needed something light after my last read, and this was perfect. It's written in Forsyth's usual dryly hilarious style and for such a small volume (171 pages including the index) it's chock full of Christmas facts. Spoiler alert: almost none of the Christmas traditions we know and love today are tied to paganism. If you want to know how this can be true, read the book. It won't be a waste of your time, and you'll probably laugh at least once along the way.
If you do read it, make sure you skim the index at the end. It might be the funniest index I've ever read (and I've been known to skim more than a few).
Pagan myths: see