The Cook. Harry Kressing.
Random House: 1965.
This has been on my 'to read' shelf for at least two years. I'm glad I got to it (rather than giving up), as it goes into the permament collection.
A tall, thin, mysterious man comes to town to apply for a job as the cook at an estate. There are two families in the area, and when they inter-marry, they will be able to move into a large castle. Gradually, through means both sly and harsh, he succeeds in having the town kow-tow to his needs, the staff at the house fired, and his employers become the butler (the father), housekeeper (the mother) and cook (the son.) He marries the daughter, and after the son marries into the other family, they all move into the castle -- after which, the son's bride dies.
Conrad, the cook, is an awesome character, clearly possessed of demonic power (if not Satan himself, on a little holiday), yet always seeming to accomplish things by verbal and culinary methods. Funny and suspenseful; difficult to accomplish. Excellent book.