C Is for Christmas: The History, Personalities, and Meaning of Christ's Birth by Warren W. & David W. Wiersbe
père et fils is their literal A-Z trivia-explanation-type reference guide which traces the backstory and symbolism of many Christmas-related tales and traditions, mostly via tracking the biblical stories, but also with some other sources and commentary as well, free courtesy of Christian publisher Baker Books.
Though heavily Scripture-reference-oriented, this is actually pretty nifty, and may well be of interest even to non-religiously-oriented secular people who might be curious about the history of certain traditions and such.

<-- they totally ignore Santa, though
And ahahaha, they go in on people who wrongly claim that the use of "Xmas" is a quote-unquote "War on Christmas" usage which is meant as a secular diss.
The latter portion of that apparently common assertation in the States (I've never heard it in Canada, but then we have a really low religiosity rate to begin with and everyone is mostly happy to say "Happy Holidays" because there are just so many in wintertime) may actually be true in some cases, but even an atheist like me knows that the X comes from the use of the Greek letter "chi" χ which in combination with "rho" ρ has long been used as abbreviation for the phrase Christ Has Risen in
koine, IIRC. And that's why that Eastern Orthodox Easter pasha cake or whatever they call it has "XB" embossed on its side, just so you know*.
So I'd give them

for that alone, even if the rest of the book weren't reasonably interesting to begin with.

<-- also not among the chosen entries but it turns out we have a consolation smiley for that:
Currently free, probably just for one day @
B&N (also
UK),
Amazon UK (slated to drop in the
main store after midnight Pacific Time),
Kobo &
iTunes &
Google Play (all available to Canadians), and
Christian Book (ADE-DRM ePub available worldwide).
Description
Throughout the centuries, so many traditions have woven themselves into the celebration of Christmas that it's difficult to understand just what the season of Christ's birth is all about.
Now beloved writer Warren W. Wiersbe and his son, fellow pastor David W. Wiersbe give adults their very own A to Z Christmas primer, cutting through the wrapping paper and pretty bows to expose and explain the backgrounds and reasons for our various symbols and traditions.
From angels and Bethlehem to yuletide and Zechariah, the information in this unique collection is sure to enlighten. Anyone who wants to have a deeper understanding of Christmas will love this insightful resource.
* I learned this useful lesson from the excellent and recommended vintage Time-Life Foods of the World international cookbook culture & travelogue & recipe series†, which unfortunately my parents didn't get all the volumes of from their apparently short-lived subscription before I was born, but can be found via most libraries which haven't turfed their collections of useful older titles.
† Cool, it has its own
Wikipedia entry. I would buy the lot of these in a heartbeat if they showed up again in paper or e-book format.

At a reasonable and preferably couponable occasionally discounted sale price, mind you.