Hooper published a number of poetry books and non-fiction and fiction titles.

His most notable poetry titles are A Map of Morning (1964), Journey Towards an Elegy (1969), Earth Marriage (1972) and Selected Poems (1977). He also published a collection of short stories entitled The Goat Paddock and other stories (1981). New Zealand artist Colin McCahon painted a series of works based on Hooper's poem 'Notes in the Margin' from Journey Towards an Elegy.

Hooper wrote a futuristic trilogy with a conservation message consisting of A Song in the Forest (1979), People of the Long Water (1985) and Time and the Forest (1986).

His two most notable non-fiction titles were a family history entitled The Seas Between (1990) and Shade of the Mugumo Tree: a Kenyan Journey (1990), about a visit he made to Kenya to visit a young man who he had sponsored.

Hooper was actively involved in the early conservation movement in New Zealand, publishing Our Forests Ourselves in (1981). He was also a member of the Forest and Bird Society and the Maruia Society.

Hooper was a great influence on a number of New Zealand writers, including Brian Turner and Jeffrey Paparoa Holman. A biography is currently being written by Pat White, a former pupil.