from zak cope's divided world, divided class.

on class:

...class denotes a dynamic social relationship corresponding to the system of ownership, the organization of labour and the distribution of material wealth as mediated by ideological, cultural and political institutions and practices. Above all, class is the product of political practices, with the relationship between the state and class struggle revolving around the issue of class domination.

cope explains:

The bourgeoisie is that group in society which directly (through full or part ownership of the means of production) or indirectly (through being paid super-wages ) depends upon the exploitation of workers for the maintenance of its income. The working class is that group in society which sells its labour-power in order to make a liv­ing. The proletariat is that section of the working class creating val­ues under industrial (urban or rural) conditions which owns none of the means of production and is forced to subsist entirely upon wages equivalent to the value of labour-power.

The labour aristocracy is that section of the working class which bene­fits materially from imperialism and the attendant superexploitation of oppressed-nation workers. The super-wages received by the labour aristocracy allow for its accrual of savings and investment in proper­ty and business and thereby “middle-class” status, even if its earnings are, in fact, spent on luxury personal consumption.

The labour aristocracy cannot, however, be wholly equated with the middle class or petty bourgeoisie. Although the labour aristocracy forms part of the middle class, the middle class also encompasses self-employed property-owners, shopkeepers, small businessmen and professionals whose income largely does not derive from wage labour and whose characteristic ideology is bourgeois.

and lastly:

Ultimately, however, the embourgeoisement of the proletariat, that is, the creation of a middle-class working class, is a political question centred on increasing superexploitation. That is the explanation for the appearance and continued existence of a wealthy working class in the world s core nations. Imperialist national oppression is both the most crucial “historical and moral element” of global wage differen­tials and the sine qua non for working-class conservatism.

That's the simple way of looking at it, but things have a tendency to become more complicated. There's talk of labor aristocrats and petite bourgeoisie for a reason.
Hitlers first and most ardent supporters were generally middle class. I'll see if I can find so e English literature on it