J.R.R. Tolkien is renowned for his groundbreaking high fantasy works, most notably 'The Lord of the .Rings' trilogy and 'The Hobbit.' These works are seminal in the fantasy genre, providing a richly detailed universe, Middle-earth, filled with diverse cultures, languages, and histories. Tolkien's creation of an entirely new mythos, including the comprehensive 'Silmarillion,' has left a lasting impact on fantasy literature and storytelling.