Some excerpts from the text that i consider particularly poignant:

“We have to begin with as precise and full a definition of imperialism as possible. Imperialism is a specific historical stage of capitalism. Its specific character is threefold: imperialism is monopoly capitalism; parasitic, or decaying capitalism; moribund capitalism”

"The fact that imperialism is parasitic or decaying capitalism is manifested first of all in the tendency to decay, which is characteristic of every monopoly under the system of private ownership of the means of production. […] Secondly, the decay of capitalism is manifested in the creation of a huge stratum of rentiers, capitalists who live by “clipping coupons”. […] Thirdly, export of capital is parasitism raised to a high pitch. Fourthly, “finance capital strives for domination, not freedom”. Political reaction all along the line is a characteristic feature of imperialism. Corruption, bribery on a huge scale and all kinds of fraud. Fifthly, the exploitation of oppressed nations […] and especially the exploitation of colonies by a handful of “Great” Powers, increasingly transforms the “civilised” world into a parasite on the body of hundreds of millions in the uncivilised [Comment: Lenin previously correctly put the word “civilized” in quotation marks, he should have done the same with “uncivilized” here] nations. […] A privileged upper stratum of the proletariat in the imperialist countries lives partly at the expense of hundreds of millions in the uncivilised [see above] nations"

“Advancing this definition of imperialism brings us into complete contradiction to K. Kautsky, who refuses to regard imperialism as a “phase of capitalism” and defines it as a policy “preferred” by finance capital, a tendency of “industrial” countries to annex “agrarian” countries. Kautsky’s definition is thoroughly false from the theoretical standpoint. What distinguishes imperialism is the rule not of industrial capital, but of finance capital […] Kautsky divorces imperialist politics from imperialist economics, he divorces monopoly in politics from monopoly in economics in order to pave the way for his vulgar bourgeois reformism […] The whole purpose and significance of this theoretical falsity is to obscure the most profound contradictions of imperialism and thus justify the theory of “unity” with the apologists of imperialism, the outright social-chauvinists and opportunists”

“[…] the opportunists (social-chauvinists) are working hand in glove with the imperialist bourgeoisie precisely towards creating an imperialist Europe on the backs of Asia and Africa, and that objectively the opportunists are a section of the petty bourgeoisie and of a certain strata of the working class who have been bribed out of imperialist superprofits and converted to watchdogs of capitalism and corruptors of the labour movement.”

“Because monopoly yields superprofits, i.e., a surplus of profits over and above the capitalist profits that are normal and customary all over the world. The capitalists can devote a part (and not a small one, at that!) of these superprofits to bribe their own workers, to create something like an alliance (recall the celebrated “alliances” described by the Webbs of English trade unions and employers) between the workers of the given nation and their capitalists against the other countries.”

“A handful of wealthy countries […] have developed monopoly to vast proportions, they obtain superprofits running into hundreds, if not thousands, of millions, they “ride on the backs” of hundreds and hundreds of millions of people in other countries […] The bourgeoisie of an imperialist “Great” Power can economically bribe the upper strata of “its” workers […]”

"On the economic basis referred to above, the political institutions of modern capitalism—press, parliament associations, congresses etc.—have created political privileges and sops for the respectful, meek, reformist and patriotic office employees and workers, corresponding to the economic privileges and sops. Lucrative and soft jobs in the government or on the war industries committees, in parliament and on diverse committees, on the editorial staffs of “respectable”, legally published newspapers or on the management councils of no less respectable and “bourgeois law-abiding” trade unions—this is the bait by which the imperialist bourgeoisie attracts and rewards the representatives and supporters of the “bourgeois labour parties”.

The mechanics of political democracy works in the same direction. Nothing in our times can be done without elections; nothing can be done without the masses. And in this era of printing and parliamentarism it is impossible to gain the following of the masses without a widely ramified, systematically managed, well-equipped system of flattery, lies, fraud, juggling with fashionable and popular catchwords, and promising all manner of reforms and blessings to the workers right and left—as long as they renounce the revolutionary struggle for the overthrow of bourgeoisie."

And finally if you take nothing else out of this remember his conclusion:

"Neither we nor anyone else can calculate precisely what portion of the proletariat is following and will follow the social-chauvinists and opportunists. This will be revealed only by the struggle, it will be definitely decided only by the socialist revolution. But we know for certain that the “defenders of the fatherland” in the imperialist war represent only a minority. And it is therefore our duty, if we wish to remain socialists to go down lower and deeper, to the real masses; this is the whole meaning and the whole purport of the struggle against opportunism. By exposing the fact that the opportunists and social-chauvinists are in reality betraying and selling the interests of the masses, that they are defending the temporary privileges of a minority of the workers, that they are the vehicles of bourgeois ideas and influences, that they are really allies and agents of the bourgeoisie, we teach the masses to appreciate their true political interests, to fight for socialism and for the revolution through all the long and painful vicissitudes of imperialist wars and imperialist armistices.

The only Marxist line in the world labour movement is to explain to the masses the inevitability and necessity of breaking with opportunism, to educate them for revolution by waging a relentless struggle against opportunism, to utilise the experience of the war to expose, not conceal, the utter vileness of national-liberal labour politics."