Since I'm tagged, I'll make a contribution. None of us are really talking about the book, so here's the summary:
None of the "talking points" surrounding Piketty's work are particularly original. What makes his book unique is that his survey of countries' return on all investments relative to the national growth rate, which is a nice bit of data collection.
According to Piketty, return on investments generally averages out at around 5%. So when overall growth is less than 5%, the income gap grows. The poor don't necessarily get poorer, but the rich do get richer. Piketty's solution is a global wealth tax that would prevent large transfers of inherited wealth and theoretically boost growth.
There are several interesting issues though. For example, even though return on investment is GENERALLY 5%, it may not be 5% in any particular case. Furthermore, a global tax on wealth sounds very coercive. Piketty's goal could be just as easily accomplished by a higher land tax or intellectual property reform (read: tax). Another solution would be to increase growth directly by liberalizing immigration policy and supporting higher birth rates.
In general, I agree that large concentrations of wealth tend to breed a coercive environment and challenge the rule of law . . . which offends my right-of-center sensibility.
But a global wealth tax is an unrealistic and even MORE coercive way to achieve that goal.
Libertarians and conservatives shouldn't find much of a problem with Piketty's analysis of wealth and return on investment. It's the "global wealth tax" that's sort of off the cliff.