This is one of my favorite books (and I found out about it through a comment like yours on HN). All the ideas were well thought out, plausible and mind-blowing.

This is one of my favorite books (and I found out about it through a comment like yours on HN). All the ideas were well thought out, plausible and mind-blowing. I especially love the way he explored how social interactions could change in a society made up of people who are really immortal computer simulations. A leader changing their apparent age during parts a speech to suit the tone, the same way someone today would shift between a large smile or stern expression based on what they're delivering. Or the couple having an argument, visibly presenting themselves as standing face-to-face, yet neither of them is able to really look at each other with their actual "viewport" (and neither of them is aware if the other is doing this). I just might have to re-read it this weekend :) Or Axiomatic, as wyager suggests, I haven't read any of those stories yet.