Beowulf stands as the oldest epic tale in any modern European language. Serving as the main inspiration for Gardner's Grendel, it is sure to captivate readers who appreciated Gardner's rendition. One notable translation is by Charles W. Kennedy, published by Oxford University Press in 1940. This edition also features a useful introduction that includes sections on its historical context, the manuscript's history, and the impact of the classical epic and various folk traditions.

Gardner's most renowned nonfiction work, On Moral Fiction (1978), delves into the purpose and craftsmanship of fiction, essentially outlining Gardner's philosophical views. The book is passionate and direct in tone, sometimes even contradictory, appealing to those who shared Gardner's belief in the profound humanity of great literature. However, it also stirred controversy among critics who thought his critiques of some contemporary novelists were overly severe.

In The Sunlight Dialogues (1972), Gardner examines the theme of order versus chaos on a grand scale, featuring eighty characters and a complex storyline set in his hometown of Batavia, New York. David Cowart, writing in the Dictionary of Literary Biography, described it as "possibly his finest" work. The novel contrasts the Sunlight Man, a capricious and enigmatic criminal symbolizing absolute freedom, with Fred Clumly, a local police officer who champions law and order.

The Legacy of Heorot (1987) offers a science fiction twist on the initial part of Beowulf, set on Earth's first stellar colony. Initially a paradise, the colony soon faces terror as dogs and cattle begin vanishing, consumed by a monstrous creature. Authors Larry Niven, Jerry Pournelle, and Steven Barnes collaborate to craft a gripping horror story reminiscent of Stephen King's style.