The social, political and cultural pressures involved with Christmas are enormous - and they operate even on those who are already inclined to celebrate it. The result is that Christmas becomes invested with so many expectations and hopes that it simply cannot live up to them, leading in the end to disappointment and depression.
Instead of a backlash against the holiday industry and the holiday itself, however, we get a backlash against critics and skeptics. They are saddled with labels like Scrooge and Grinch and treated like they have some sort of psychological disorder - why else would they dare to criticize such a revered American tradition? This is what makes a book like Flynn's so important; he lays out his case about Christmas clearly and thoughtfully, forcing others to engage the issues on the field of ideas rather than polemic.
The first part of Flynn's book relates the history of Christmas and Christmas traditions. Other books do the same, but the information is not redundant here. One aspect of Flynn's argument that Christmas should not be so dominant in American culture is the fact that so much of isn't really very old or "traditional" to begin with. This doesn't mean that the celebration of Christmas is recent, however.
Many people are simply unaware of the fact that, in the English speaking world, Christmas was very nearly killed off by Protestant "fundamentalists" - Puritans who objected to Christmas so much that, wherever they held power, they passed laws banning it. Even after they lost power, they had succeeded in getting people out of the habit of celebrating, effectively breaking the tradition of Christmas. The result is that the Christmas we know today is a recreation - even the oldest elements have been reworked and rethought in order to serve modern purposes.
http://atheism.about.com/od/bookreviews/fr/TroubleXmas.htm-------------------------------------
I had the privilege of listening to Tom give a lecture on this just a couple of weeks ago. Versions of it are widely available on youtube and I highly recommend having a look or reading his book.