Hi, I love Kate Morton too. Have you read her most recent novel, The Distant Hours? It is probably my favourite of the three she has written.
I see that you've already read The Thirteenth Tale, which would have been one of my recommendations. As a KM fan, others that I'd recommend are The Unseen by Katherine Webb (I've just finished this and I LOVED it), The Observations by Jane Harris and Hothouse Flower by Lucinda Riley.