From 1920 ’til 1943, Tolkien wrote letters to his four children (over an age range of 12 years), as from Father Christmas; with shaky writing from the cold, suitable North Pole stamps and postmarks, and hand-drawn illustrations to accompany them.
In the 1976, three years after he died, his daughter-in-law compiled these into a book for people to enjoy, and last year, to mark the centenary of the first letter, this edition was published.
He shares stories of things going on in the North Pole, with his companion the Polar Bear, problems every few years from goblin attacks, and these are also covered in the illustrations. He uses these some years to explain why they might not get what they expect, but always acknowledges the letters they’ve written too.
It’s a lovely warm hug to read over the Christmas period, I saw that someone said they read one letter to their kids every night over advent as a build up to Christmas Day, which I thought was quite sweet!

Anything to add...?