Gatheru was born to a squatter family living on a European farm. He attended medical school in Nairobi, but was forced to continue his education abroad after he protested the treatment of Africans by the colonial rulers. After a year in India, he spent eight years from 1950 in the United States before studying law in England. He returned to Kenya when it gained independence in 1963.
He taught African and Middle Eastern history for many years at California State University in Sacramento.
- A Child of Two Worlds: a Kikuyu's story, 1964
- Kenya : from colonization to independence, 1888-1970, 2005
- From beneath the tree of life : a story of the Kenyan people of Ngai, 2005
- Simon Gikandi, 'Gatheru, Mugo', in Gikandi, ed., Encyclopedia of African Literature. Routledge; 2002. ISBN 978-0-415-23019-3. Reprinted online here
- Fetter, B., Colonial Rule in Africa, 1979, p.191
- Obituary for "Prof. Reuel Mugo-Gatheru" [sic], Sacramento Bee, 27 November 2012. Accessed 17 August 2020 via legacy.