While much of Kinnell's work has been regarded as dealing with social issues, it is by no means confined to one subject. Some critics have pointed to the spiritual dimensions of his poetry, as well as the natural imagery present throughout his work.[10] For instance, "The Fundamental Project of Technology" deals with all three of those elements, creating an eerie, chant-like and surreal exploration of the horrors atomic weapons inflict on humanity and nature. Kinnell occasionally utilized simple and brutal images ("Lieutenant! / This corpse will not stop burning!" from "The Dead Shall be Raised Incorruptible" in The Book of Nightmares) to convey his anger at the destructiveness of humanity, informed by his activism and love of nature. Scholars have also identified, on the contrary, themes of optimism and beauty in his use of language, especially in the large role animals and children have in his later work, evident in poems such as "Daybreak" and "After Making Love We Hear Footsteps".[11]
In addition to his works of poetry and his translations, Kinnell published one novel (Black Light, 1966) and one children's book (How the Alligator Missed Breakfast, 1982).
Kinnell wrote two elegies for his close friend, the poet James Wright, upon the latter's death in 1980. They appear in From the Other World: Poems in Memory of James Wright.
Kinnell's poem The Correspondence-School Instructor Says Goodbye to His Poetry Students was excerpted in Delia Owens’ novel Where the Crawdads Sing, as a goodbye note left by the protagonist’s mother who left her at a young age.
