I thought Class Warfare was going to be a rules-lite approach to creating classes for DungeonWorld, rather along the lines of the variant rules for races in Dark Heart of the Dreamer. This was my preconception of the book and I'm not going to hold it against it that Class Warfare is something subtly different. It is a toolkit for deconstructing the existing classes into components that can be used together to create new playbooks and also a rich source of new moves.
The technical analysis of how DungeonWorld's class playbooks work is excellent and worth a read for anyone interested in game design (particularly of DungeonWorld playbooks) and the relative merits and flaws of DungeonWorld in particular.
With that done the book then moves onto an example new playset and illustrates how the book is to be used to construct new character classes.
The bulk of the book is made of various classes that are tighter in scope that the ones in the main rulebook. Most of the main book classes are decomposed into smaller parts that can then be reassembled.
It certainly gives players who are tired of the class tropes of the core game a chance to create something more distinctive and from a design point of view actually moves the Apocalypse System away from tight playset designs aiming to shape the actors in the game world to a more simulation-based ability to reflect the desires of the player to create and explore a certain character and set of powers.
Basically Class Warfare is sitting on the opposite end of the spectrum to Sagas of the Icelanders. It gives the player agency to bring their favoured brand of fantasy into the game rather than that defined by RedBox D&D.
I feel equivocal about DungeonWorld and I keep looking for the design that is going to unlock all the good parts of the game and ditch the boring aspects. Class Warfare isn't that key but at a forensic decomposition of how player interaction works in the game its a valuable piece of game design in Apocalypse World family.