The main themes include coming - of - age. Augie experiences a lot of growth and development. Social mobility is also there. He moves through different social strata, showing how society functions. And there is a sense of identity formation. He tries on different 'identities' as he has different jobs and meets different people.
Well, I think a major theme is the search for meaning. Augie is on this long journey where he's trying to figure out what the purpose of his life is. Additionally, the theme of love and loss is present. He has relationships that end, and these experiences shape him. And there's the theme of freedom. He often rebels against constraints and tries to find his own path to freedom.