The Dark Child (L'Enfant Noir) by Camara Laye — a sharp, lyrical memoir of growing up in pre-independence Upper Guinea. One of the great works of francophone African literature, published in 1953 and widely translated.
Beyond the Storyteller's Magic by Ahmed Sékou Touré — for serious readers only; the strange, hectoring prose of the first Guinean president, useful as a primary source for understanding the regime that built and ruined Conakry.
Camp Boiro: Guinée 1960–1984 by Amadou Diallo — one of the principal accounts by a survivor of Touré's political prison, in French. There is no good English-language equivalent; the Camp Boiro literature is almost entirely in French.
Africa in Chaos by George Ayittey — covers Guinea among other West African states in the 1990s; sceptical, pan-African, useful for context on what the post-Touré era looked like across the region.
Sundiata: An Epic of Old Mali by D.T. Niane — not strictly about Guinea, but the founding epic of the Mandé civilisation, which underlies much of Upper Guinea's culture. Written down in the 1960s by a Guinean historian working from the oral tradition of the griot Mamadou Kouyaté.