Not all of his work is great, but the "Thousand Cultures" series and "Century Next Door" series are the great reads.

Note: The dark anti-hero in "Kaleidoscope Century" is probably the reason he hasn't won many major awards. You can't write such a character and not piss off the various sci-fi author and fandom cliches.

Agreed. Barnes can go dark - REALLY dark.

The Directive 51 universe is really dark, but has a ton of great ideas and great writing.

Thank you, I'll check them out