The State and Revolution (1917), by Vladimir Lenin, describes the role of the State in society, the necessity of proletarian revolution, and the theoretic inadequacies of social democracy in achieving revolution to establish the dictatorship of the proletariat.
The State and Revolution is considered to be Lenin's most important work on the state and has been called by Lucio Colletti "Lenin's greatest contribution to political theory"  According to the Marxologist David McLellan, "the book had its origin in Lenin's argument with Bukharin in the summer of 1916 over the existence of the state after a proletarian revolution. Bukharin had emphasised the 'withering' aspect, whereas Lenin insisted on the necessity of the state machinery to expropriate the expropriators. In fact, it was Lenin who changed his mind, and many of the ideas of State and Revolution, composed in the summer of 1917 - and particularly the anti-Statist theme - were those of Bukharin" 
Lenin's direct and simple definition of the State is that "the State is a special organisation of force: it is an organisation of violence for the suppression of some class."  Hence his denigration even of parliamentary democracy, which was influenced by what Lenin saw as the recent increase of bureaucratic and military influences: "To decide once every few years which member of the ruling class is to repress and crush the people through parliament - this is the real essence of bourgeois parliamentarism, not only in parliamentary-constitutional monarchies, but also in the most democratic republics" 
Citing Friedrich Engels and Karl Marx, Lenin clarifies theoretical questions about the existence of the State after the proletarian revolution, addressing the arguments of anti-authoritarians, anarchists, social democrats, and reformists, in describing the progressive stages of societal change — the revolution, establishing “the lower stage of communist society” (the socialist commune), and the “higher stage of communist society” that will yield a stable society where personal freedom might be fully expressed.
Lenin especially defends Marx’s theory of Communism, and Marxism generally; to wit, when old revolutionaries die, the bourgeoisie are not content with labelling them “enemies of the state”, because that would attract political radicals, so they attack the revolutionaries’ theoretic writings by ascribing to them an (anti-revolutionary) social-democratic mediocrity contrary to “the revolutionary nature of Marx”; such bourgeois intellectuals are the “revisionists” who transform a human being into an abstraction:
During the lifetime of great revolutionaries, the oppressing classes constantly hounded them, received their theories with the most savage malice, the most furious hatred, and the most unscrupulous campaigns of lies and slander. After their deaths, attempts are made to convert them into harmless icons, to canonize them, so to say, and to hallow their names, to a certain extent, for the ‘consolation’ of the oppressed classes, and with the object of duping the latter, while, at the same time, robbing the revolutionary theory of its substance, blunting its revolutionary edge, and vulgarizing it. Today, the bourgeoisie and the opportunists within the labour movement concur in this doctoring of Marxism. They omit, obscure, or distort the revolutionary side of this theory, its revolutionary soul. They push to the foreground and extol what is, or seems, acceptable to the bourgeoisie. All the social-chauvinists are now ‘Marxists’ (don’t laugh!). And more and more frequently, German bourgeois scholars, only yesterday specialists in the annihilation of Marxism, are speaking of the ‘national-German’ Marx, who, they claim, educated the labour unions, which are so splendidly organised for the purpose of waging a predatory war!
The State and Revolution describes the inherent nature of the State as a tool for class oppression, a creation born of a social class’s desire to control the other social classes of its society when politico-economic disputes cannot otherwise be amicably resolved; if a dictatorship or a democracy, the State remains the social-control means of the ruling class. Even in a democratic capitalist republic, the ruling class never relinquish political power, maintaining it via the “behind-the-scenes” control of universal suffrage — an excellent deception that maintains the idealistic concepts of “freedom and democracy”; hence, communist revolution is the sole remedy for such demagogy:
(i) The anarchists propose the State’s immediate abolishment; Lenin counter-proposes that such idealism is pragmatically impossible, because the proletariat would need to crush the bourgeois resistance through a mechanism, and that is the state.
(ii) Were the State immediately abolished, without the “conditions leading to the arising of the State” being abolished as well, a new State would appear, and the socialist revolution would have been for naught.
In the event, the proletariat through the dictatorship of the proletariat would establish a communal State (per the 1871 Paris Commune model), then gradually suppress the dissenting bourgeoisie, in achieving the withering away of the State as its institutions begin to “lose their political character”.
Thus, following Marx's conclusions on the Paris commune, which Lenin took as his model  Lenin declared that the task of the Revolution was to smash the State. Although for a period under communism, "there remains for a time not only bourgeois right but even the bourgeois State without the bourgeoisie,"  Lenin believed that after a successful proletarian revolution the state had not only begun to wither, but was in an advanced condition of decomposition. But Lenin also called the state "the armed and ruling proletariat" so McLellan asks whether this, too withers? Yes, according to McLellan, "in so far as it was in any way a power separate from and opposed to, the masses"  Lenin had little to say of the institutional form of this transition period. There was a strong emphasis on the dictatorship of the proletariat: "A Marxist is solely someone who extends the recognition of the class struggle to the recognition of the dictatorship of the proletariat. This is what constitutes the most profound distinction between the Marxist and the ordinary petty (as well as big) bourgeois. This is the touchstone on which the real understanding and recognition of Marxism is to be tested."