Jacobin has the article Piketty’s Capital in the Twenty-First Century shows that not everything in mainstream economics is worthless. I am not sure the headline is the best representation of what is in the article.
Piketty suggests that the rise is a long-term structural trend – the outcome of decelerating population and productivity growth coupled with a profit rate (r) that stays steady. But what keeps r high? Piketty never explicitly says. This question is at the heart of the struggle over how to interpret his book.
Since I have not read the book yet, I have no idea if the reviewer is fairly representing what Piketty says. However, I think the review is an excellent discussion of this multifaceted issue, no matter what Piketty might have said.