Pannekoek's book is heavily marked by the time of its writing in late 1930s. His criticism of Lenin is predicated on viewing the Soviet Union, where the Stalinist show trials were in action, as essentially part of Lenin's legacy. While his critique of Lenin was devised earlier, it is actually part of Council Communism critique of party Communism. However, his criticism of Lenin "as philosopher" is curiously narrow in terms of philosophical thinking as well as literal reference. Apart from his useful comments on Lenin's background, pointing out the backwardness of Russian society in the early 20th century, still a Tsarist absolute state, and Lenin's and Plekhanov's need to theoretically combat religion, not bourgeoisie, Pannekoek's critique too much relies on identifying Lenin of 1908 with his complete philosophical position. This identification is false. However, before digging further into Lenin, some true merits of Pannekoek are to be mentioned. I quote Kevin B. Anderson's book "Lenin, Hegel, and Western Marxism":
In his 1912 dispute with Kautsky over revolutionary tactics, Pannekoek attacks the latter for referring to unorganized (nonunionized) workers as "motley masses." Pannekoek argues that what is most important is not formal membership in a union or a party but rather "the spirit of organization," the sense of being bound together in the quest for a "new humanity" (59). He writes further that "irrespective of all assaults upon the external forms of association, the masses in which this spirit dwells will always regroup themselves in new organizations" (57). Pannekoek also attacks Kautsky for wanting socialists merely to take over the state: "The struggle of the proletariat is not simply a struggle with the bourgeoisie over the state power as object, but a struggle against state power . . . the content of this revolution is the destruction of the instruments of power of the state and their dislodgement [Auflösung] with the aid of the instruments of power of the proletariat . . . The struggle ceases only when, as the end result of it, the state organization is completely destroyed." (p.152)
As Anderson notes, Lenin was influenced by Pannekoek and I think any contemporary leftist thinker should be too. That said, the Lenin of Pannekoek's book is a caricature, and no justice to him is done if Pannekoek's vindictive accusations are to be taken for truth. In setting things at more even footing, Lance Byron Richey's introduction is quite useful.
Curiously, written in 2003, Richey's introduction already seems to come from a different era. Last fifteen or so years have shown a growing interest in Lenin as an undercurrent influence to "philosophy of event" and "new materialism" through the post-Maoist French militant philosophy (Althusser, Badiou, Balibar, Rancière). Reference to Lenin is continually made by Zizek, of course, but he is also a name that Brassier, Coombs, and Bosteels come back to. Excluding the more scholarly work of Anderson, who is interested in the 1914-1915 Hegelian writings of Lenin and his influence on the dialectical thought of Western Marxism, the recent point has been more on the Lenin as political strategist and tactic.
Lenin's political shrewdness at the helm of the Bosheviks, before, during and after the October revolution, his political mastermind in revolutionising history - these are the very characteristics that 80s and 90s Thatcherite unpolitical academia so abhorred and projected to all of Marxism. In the 21st century this is the Lenin that has come back at least as an intellectual figure, if not organisational principle. The political movements of the left have been more anarchist in general tendency after the fall of the Berlin wall, I presume. The pamphlet "What is to be done?" has been key to the new materialists, and there is a connection from it to Lenin's 1908 writings, the object of Pannekoek's critique.
Translator of the book, Lance Byron Richey suggests that Lenin's fierce critique of Bogdanov's Machism and Lunacharsky's spiritualism is not interesting only in terms of history of ideas, but might have contemporary philosophical relevance. This it his case. What seems in "Materialism and Empirio-criticism" as Lenin's relapse into naive realism might is predicated on revolutionary intent not to be bogged down by philosophical disputes or hair-splitting with no real effect. In fact Lenin is adamant in his quest to liquidate false problematics and keep the party intellectuals on the right path. Siding with Marx and Engels against empiricist tradition (positivism, Machism, etc.), Lenin argues that our knowledge is “reproduction” or “photograph” of the external world, or that “our sensation, our consciousness is only an image of the external world". (Richey, p.44)
The point behind Lenin's minimal epistemology is its design to weed out all effects of representations, or introducing contingent signs between objective reality and consciousness. This has surprising connection to what Quentin Meillassoux has critiqued as different forms of "correlationism", or the post-Kantian situation where all talk of "arche-fossil", of a non-knowable object becomes an embarrassment for intellectual knowledge. Lenin in fact has an argument that has the same form and intent, in his book. The argument is the following: if natural history tells us of times, when there was no life on Earth, can we say that there were real events, and natural phenomena, without anyone's experiencing them? Lenin's answer is: of course these events without beholder were real, because human being is part of nature, and not the other way around. Instead of entering into other standard discussions of epistemology (e.g. how do we know that what we see is we think we see?), Lenin refuses to take these questions seriously. For him the most important thing is not philosophical rigour, but political capability. The revolution must be seen as an objective goal, and there must be no mistaking its signs. Thus any contingency or randomness between reality and its representations is not be allowed.
I will probably pursue this line of thought in more detail somewhere else, but despite its philosophical shortcomings and rather tiresome ire towards philosophical adversaries, I think Lenin's 1908 book on materialism should be studied in the 20th century as an example of how to actually make philosophy politically relevant, instead of silencing politics through philosophy. Paradoxically, Pannekoek's polemics against Lenin might be a good place to start with this project, especially when put in context by Richey's introduction. In conclusion, I would side with Mayakovsky, who writes in 1924, after Lenin's death, in the avant-garde art journal LEF: "Lenin is still our contemporary".