With this work, written in the first six months of 1916, V.I. Lenin revealed the economic and political essence of imperialism, the new stage of development into which capitalism entered at the beginning of the 20th century. Lenin summarizes significant conclusions from the development of capitalism in the nearly fifty years that had elapsed since the publication of the first volume of Marx's Capital.

The book consists of 10 chapters, with the first 6 providing a scientific analysis of the economic essence of imperialism and the remaining 4 offering a general overview of imperialism. Lenin contrasts his views with those of various opportunists – foremost among them Kautsky – who regarded imperialism as a policy of the ruling class rather than a stage of capitalist development associated with the dominance of monopoly in capitalist production, the fusion of industrial and banking capital, the export of capital, and the economic character of imperialist wars (the division and re-division of markets). The maturation of capitalist societies in their imperialist stage of development entails the maturation of the material prerequisites for socialism, opening a long historical period characterized as the era of transition from capitalism to socialism.