Harry Johnston's A History of the Colonization of Africa by Alien Races is an ambitious imperial survey of the successive peoples who entered, settled, and ruled parts of the African continent from antiquity to the modern era. Blending historical synthesis, ethnographic speculation, and geographical description, Johnston writes in the expansive, authoritative prose characteristic of late Victorian and Edwardian imperial scholarship. The book belongs to a moment when European writers sought to systematize Africa's past through the lenses of race, migration, and empire; as such, it is both a substantial compendium of information and a revealing document of its intellectual age. Johnston (1858–1927) was not merely an author but a central actor in Britain's imperial project: explorer, colonial administrator, linguist, naturalist, and prolific writer. His experience in East and Central Africa, especially in territories such as Uganda and British Central Africa, profoundly shaped his historical imagination. The book reflects his conviction that Africa's history must be read through long patterns of external contact, movement, and domination, while also displaying the taxonomic habits and racial theories common to his period. This is a valuable book for readers interested in African historiography, imperial knowledge, and the history of ideas. It should be read critically, but precisely for that reason it remains indispensable: not only for what it records about Africa, but for what it reveals about how empire interpreted the continent.