First in the 1990's when I first read his work. Now as an author for The Atlantic.
His writing is prolific yet clear.
He's also a realistic libertarian. And when the facts could not support his opinion he then changed his opinion. Which is difficult. I went through a similar transformation politically. But I am not as smart as Judge Posner so I cannot explain it as well.
See his interview at Harper's: Six Questions for Richard Posner on Capitalism and Crisis