King Lear offers some pretty insightful social commentary on everything from class and politics, homelessness, mental illness, the system of primogeniture, the tensions between youth and the older generation, and so on. For many, the play seems to challenge and critique some existing (sixteenth and seventeenth century) social and political structures while offering some radical solutions. For others, the play takes a good hard look at England's social ills but eventually winds up supporting the status quo.
Edmund is one of Shakespeare's most complex villains because he has a strong motive for his evildoing – his status as an illegitimate son is always rubbed in his face.