In a contemporary town in the American Midwest where he has no connections, an educated man recently released from prison is staying in a motel. He writes letters to his brother and to others, including a friend still in jail. When he meets a real estate agent who tells him he is the heir to a huge old house, long empty, he moves in, though he is too broke to even buy furniture, and is immediately confronted by supernatural and fantastic creatures and events.
His life is utterly transformed and we read on, because we must know more. We revise our opinions of him, and of others, with each letter. We learn things about magic, and another world, and about the sorcerer Mr. Black, who originally inhabited the house.
And then perhaps we read it again.