These three books probably cover most, if not all, of the art JRR Tolkien created for Middle-Earth: "The Art of The Hobbit" (the book mentioned in the link), "T

These three books probably cover most, if not all, of the art JRR Tolkien created for Middle-Earth: "The Art of The Hobbit" (the book mentioned in the link), "The Art of The Lord of the Rings" and "Tolkien: Maker of Middle Earth".