Norstrilia I absultely second. Actually, all of Cordwainer Smith is worth a read, but stories set in The Instrumentality of Mankind certainly are.

The culture novels by Iain M. Banks are also amazing, ship names in particular, but also themes.

And then there is The Hitchhiker's Guide to the Galaxy (or is this too recent) another fine example of exploring the absurdity of mankind.

I often find that older works deal more with ideas and philosophy than the modern works, which tend to be more formulaic with some notable exceptions, like K. J. Parker and Adrian Tchaikovsky - there are less niche works - or so I feel.