The Dutch-German Communist Left, represented by the German KAPD-AAUD, the Dutch KAPN, and the Bulgarian Communist Workers Party, separated from the Communist International in 1921, and famously attracted the ire of Lenin, who wrote his Left Wing Communism in response. Drawing on a wide breadth of first hand material, this volume examines the history, ideas, and legacy of this tendency.
Essential reading for tracking the political history of left-communism following expulsions from the comintern in 1926. That said, you have to follow a ton of party splits, mergers, factional disputes throughout, which means its not easy reading. The fact that it's not strictly organized by chronology also requires you to expend some effort figuring out when what you're reading is taking place and recalling previous narratives that overlap with the current one.
Interesting read, but you can tell when the author himself gets bored of the constants splits and just starts listing events and dates like it's a chronicle (to be fair: it may also be that the splits were so unremarkable that there was little material to discuss).
Also, he tends to criticize arguments for "deviating" from "Marxism". That might very well be true for him, but just stating that something or someone isn't Marxist isn't exactly what I'd call an insightful critique. This applies especially to his defense of communist participation in wage struggles.
Aside from that, Bourrinet is capable of juggling a bunch of different organizations, individuals and ideologies by constantly relating them back to each other, explaining con- and divergences and guiding his readers through a pretty turbulent history.
Another thing: His use of footnotes is very liberal. Basically, he crams them full of (often biographical) information about every person mentioned, however minor their involvement may be. Some might find that overwhelming, but seeing how the Dutch-German leftcommunists are little researched bunch, it's probably a good thing that Bourrinet inserts his own little archive into the work.