Reform or revolution is a great book. You definitely should read it.

Rosa’s criticism in the book is not against reform, it’s against reformism. Reformism is a strategy of gradually reaching socialism through reforms in the bourgeois political system. The problem of this strategy is its political naivety, because at any moment the bourgeoisie can turn the tables and use other tactics to quell the advance of the proletariat. This strategy has other ill effects on the proletariat like reducing the revolutionary impetus and stimulating economistic and opportunistic tendencies in the proletariat.