I think it was called The Twelve Days of Christmas ( funny time of year to be thinking of it, I know). We had it read to us at primary school (late 70s). It was basically about how each of the twelve days had a theme in "olden days". For example: Boxing Day was when you gave little boxes with gifts in to people etc. I think it was told in the form of a story as opposed to non fiction.
I've wanted to re read it for ages but if you put 12 Days of Christmas into Amazon for example, it just has books telling the verses of the song rather than this story. I would guess it was aimed at over 8s. Any bells rung? Tia.