If the birth of Jesus was the original Christmas story, the idea of Christmas is also a rich source of secular literature. Charles Dickens' A Christmas Carol comes first to mind. After Scrooge awakens from his bad dreams, his first question is: "What day is it, boy?" The answer of course comes from Tiny Tim: "Why, it's Christmas, sir!" This exchange not only sets the season, but technique-wise (in terms of opening lines) is extremely clever. In two sentences of dialogue, Dickens fleshes out the full personalities of his main characters: Scrooge must certainly be a humbug to not know that it's Christmas; Tiny Tim is an optimist-astonished that someone would not know.
Clement Clarke Moore's (1779-1863) "Twas the NIght Before Christmas" is a universally popular tale, and from the early 20th century O'Henry's chestnut, "The Gift of the Magi" (her beautiful hair, his beautiful pocket watch) is worth revisiting. Then there's Dr. Suess and his "The Grinch Who Stole Christmas" (Jim Carrey is the best film-version grinch) -- but I'm more interested in the less well-known, more literary manifestations of Christmas.
Dylan Thomas's short story, "A Child's Christmas in Wales," is both popular and literary. At 3000 words it's the perfect short piece to read aloud, and to listen to a true poet writing in prose. A companion piece is Truman Capote's "A Christmas Memory," a short story about a boy living with his aunt, and the two of them making fruitcake for Christmas. You can taste the pecans, you can feel the love.
On the lighter side but still literary, take a look at Jean Shepherd's "A Christmas Story" (there's a sweet movie version), about a boy and BB gun and more. Shepherd is a humorist, and it's a fun read with heartfelt moments that will bring back the thrill of Christmas morning.
More obliquely informed by Christmas is Eudora Welty's "A Worn Path." There are only two references to Christmas in Welty's story, neither by the main character, Phoenix Jackson. On her quest to get medicine for her ailing grandbaby she must be reminded, by a passing hunter, that, "it's Christmastime, Granny." Once cast in the context of Christmas, the story is all the more poignant.
Perhaps the best literary Christmas story is James Joyce's "The Dead." Long by short story standards, "The Dead" is rich, sad and wonderful -- as much about mortality as Christmas. Set at an Irish Christmas party, Gabriel Conroy's wife confesses, in an unguarded moment, of her love for childhood sweetheart, Michael Fury, long dead but not in her heart. First read the story, then see the marvelous film version by John Huston. It was his last film, and his daughter, Angelica Huston, plays Gretta Conroy. The scenes of the family and friends arriving at the old aunts' house -- the stomping of boots to shed snow, the clink of glasses, the obligatory "performance" by an ancient aunt of a sad Irish song, the drunken Freddy Malin (every family has one) will open your heart in the very best of ways. Which is what Christmas is all about.