Karl Marx - Karl Korsch

Thanks for this. I've only read a rough photocopy of this scanned version (before Ken Knabb formatted and edited it for his website), but Korsch's biography of Marx is the best I've ever read. Second place goes to Otto Rühle's Karl Marx: His Life and His Work, although I agree with Paul Mattick Sr.'s critique (from Anti-Bolshevik Communism) in "Otto Rühle and the German Labour Movement"
Mattick

. . . that Rühle applied his new psycho-sociological concept of Marxism [in the biography] . . . This kind of ‘historical materialism’, which searched for reasons of ‘inferiority and superiority complexes’ in the endless domains of biology, anthropology, sociology, economics and so forth in order to discover a kind of ‘balance-of-power of complexes by way of compensations’ which could be considered the proper adjustment between individual and society . . .

Korsch didn't make the same mistake.

And interesting backstory to Korsch's biography on Ken Knabb's website is that a comrade was working in the Cascade Mountains as a fire lookout, à la Jack Kerouac in the Dharma Bums, and had laptop, scanner and a photovoltaic charger and spent much of his free time scanning the whole book that he'd borrowed from Ken.

EDIT: I just added Mattick's review of Korsch's biography http://libcom.org/library/review-“karl-marx”-karl-korsch.