“Cultivator of well-placed authors, widows and heirs, Glenn Horowitz combines the curiosity of an intellectual with the instincts of a businessman. He is known for sharp elbows, unyielding persistence and the high — some say inflated — prices he extracts for his clients. Through his two galleries on the Upper East Side and in East Hampton, which he runs with the art dealer John McWhinnie, Horowitz organizes book and art exhibitions — and parties that glamorize books as luxury products and help drum up business.”