I have a few books I like to read in December, plus many children's books, but that's another post!
One book that is hilarious is Skipping Christmas by John Grisham. It was made into a movie, Christmas With the Kranks, which follows the book pretty well. Even the librarian, when I checked the book out, said she laughed out loud reading it. It is funny, pretty short, and easy to read.
I also like The Christmas Wish by Richard Siddoway. There is a second book, The Christmas Quest. I think The Christmas Wish was also made into a movie, but I haven't seen it.
And then Donna VanLiere wrote a series of books, the first one is The Christmas Shoes, it's based on the song Christmas Shoes. She has now 5 books in the series. They are pretty fast reads too.