Mission to Kala by Mongo Beti (1957) — The Cameroonian novelist Mongo Beti grew up near Yaoundé and spent his career writing about colonial and post-colonial Cameroon with a mixture of satire and anger. Mission to Kala is one of his more accessible works, following a young man sent to retrieve a runaway wife from a rural village; it is funny, sharp, and deeply rooted in the social world of Cameroon's south. Any of his novels will reframe what you see in the country.
In the Shadow of Man by Jane Goodall (1971) — Goodall's account of her years with chimpanzees in Tanzania is not about Cameroon, but anyone visiting the Limbe Wildlife Centre will find it transformative context. After watching Goodall describe chimp behaviour, tool use, and social bonds in detail, the animals at the sanctuary become individuals rather than exhibits. One of the best books written about any animal.
Primate Conservation in the Wild edited by Jane Rowe and Richard Carroll (1996) — A more technical but accessible overview of primate conservation across Africa and Asia, with chapters covering the drill and western lowland gorilla — two of the species held at Limbe. It puts the sanctuary's work in the context of what is happening to these animals across Central Africa's forests.
The Scramble for Africa by Thomas Pakenham (1991) — Cameroon's colonial history is unusually tangled: first German, then split between British and French after World War I, which is why the southwest around Limbe remains English-speaking today while the rest of the country is French-speaking. Pakenham's panoramic history of the continent's partition is the best single-volume account of how this happened and what it produced.