Lenin's famous pamphlet was an attempt to extract strategic and tactical lessons from the experience of the Russian Revolution. It was aimed at fast-tracking the development of the newly formed Communist Parties in the West, who were grappling with how to rapidly build mass revolutionary organisations in difficult conditions.
In a sharply polemical work, he argued that communists need to find ways to reach out to workers still under the influence of reformist organisations. This means being prepared to work in bourgeois parliaments and reactionary trade unions, not because those institutions can be tools of revolution, but because it is the only way to break workers from their illusions in reformism.
This flew in the face of the ultra-left tendencies dominant among the young radicals in western Europe, but Lenin’s insights had an enormous influence in shaping the early communist movement, and remain invaluable today.