About the book (from Wikipedia):
The Father Christmas Letters, also known as Letters from Father Christmas, are a collection of letters written and illustrated by J. R. R. Tolkien between 1920 and 1942 for his children, from Father Christmas. They were released posthumously by the Tolkien estate on 2 September 1976, the 3rd anniversary of Tolkien’s death. They were edited by Baillie Tolkien, second wife of his youngest son, Christopher. The book was warmly received by critics, and it has been suggested that elements of the stories inspired parts of Tolkien’s The Lord of the Rings.