I just reacquainted myself with a book I hadn't thought of since my childhood:
Story of Holly and Ivy by Rumer Godden.
What a sweet Christmas story for a young girl to enjoy. Unlike many of Godden's other books, it is not religious in nature, but the spirit of giving, sharing and love that should fill all our hearts at Christmas is abundant in this book. I handed it to Middle Sister after I finished rereading it, and Miss Reluctant Reader Herself devoured and enjoyed it as well.
I am such a fan of this author that I also reread The Kitchen Madonna yesterday. Apparently this one's out of print--but search your library! This is not a Christmas book, but what a lovely story of, again, giving, sharing and love--and how love brings a child to do what is very out of character, so that another person will have happiness.
If these books don't put you in the Christmas spirit, I don't know what will.