The Christmas letters for this year are addressed to "My dear Christopher" - his older brothers must no longer have believed in Father Christmas (though he does send his love to them), and Priscilla is included in FC's greetings, so perhaps not yet able to read and write enough for her own letter.
Correction: Hammond and Scull (in
Chronology) mention a shorter letter that Priscilla received.
The letter is not as long as those of the past years, and there are only little anecdotes told, no big exciting story. The picture shows the Christmas tree that came up to the North Pole from Norway and has magic lights (candles) of various colours.
Everything is already set up for a big party on Boxing Day, when over 100 guests will celebrate with Father Christmas and the bears.
I wonder if something kept JRRT especially busy that year, so that he couldn't concentrate on writing an elaborate story. I couldn't find anything specific in the
Chronology.