The notion of discontinuity is a paradoxical one: because it is both an instrument and an object of research; because it divides up the fields of which it is the effect; because it enables the historian to individualize different domains but can be established only by comparing those domains.
Some 'continental philosophers' are difficult to read. Derrida is a spectacularly bad writer, for instance. Foucault is not one of them however. Discipline & Punish is about as readable as Dickens IMO.