Kautsky Kautsky KAUTSKY!
This proved to be an incredibly useful read for me, defining (in Lenin's terms, of course) key concepts in Marxist theory such as "opportunist" socialism, the dictatorship of the proletariat, the bourgeois state, and (you guessed it) revolution in about 1/10th as many pages as English editions of Das Kapital Vol. 1 (I'll get to it, I swear).
Why are socialists often categorized as "revolutionary"- or "reform"-minded? Or, worse, counter-revolutionary? Why are (some of) the anarchists at odds with (some of) the Marxists? How does a state wither away? How dope was the Paris Commune? Why is Kautsky such a simp for the bourgeoise?? Ol' Lenny's got the scoop, and he's bringing it to you in plainer language than you'd expect for the early 20th century, frankly.
My only real complaint is that Lenin is pretty keen on repeating himself at various points. But given that he is restating points plainly (kudos to the translators), and with the aim of illuminating passages from Marx and Engels, I suppose it is somewhat warranted.
The Todd Chretien introduction to this edition is worth reading. While I typically skim introductions to historically important works, the historical information and outline of the following chapters led me to more careful (and less frustrated) reading.
I would recommend this to any socialist really, even my anarchist comrades. While Lenin is critical of "the anarchists" generally, it's clear he has more affinity for those that share his end goal of a stateless, classless society, than those (like the Social Democrats) who he believes claim that as the ultimate desire while actively working against achieving it. He does accuse Kropotkin and a few others, who ended up signing a particular pro-war statement, of hypocrisy, but by and large he simply disagrees with the concept of smashing the state and neglecting to build a temporary worker's state in its stead (not the shared anarchist goal of smashing the currently-existing bourgeois state).
The other useful thing about this edition are the series of short biographies of other leftists mentioned in the text, which appear at the end of this volume. Both because they help in understanding Lenin's references, and because you get to see how many bad-ass radicals did cool shit only to get executed by Stalin when he consolidated power.