Since I'm not familiar with the novel, the main characters might be a Christmas - loving woman who stumbles upon a mystery during her holiday preparations. There could also be a reclusive neighbor who turns out to be involved in the secret somehow. And maybe there's a jolly postman who delivers a mysterious letter that starts the whole adventure related to the Christmas secret.
I don't know as I haven't read it. But it could have characters like a young child who is curious about Christmas secrets, a wise old man who holds the key to the secrets, and perhaps a family trying to make their Christmas special while uncovering these secrets.
Without having read 'the christmas secret novel', it's hard to say for sure. However, it could feature a group of friends who get together every Christmas. One of them discovers something strange and they all start to investigate. There might also be a character like an old - fashioned toymaker who has a connection to the Christmas secret, perhaps having made a special toy that has a hidden meaning or power.