The short answer is what Roc Paint just posted. It's impossible to judge who has the penultimate basketball IQ in today's NBA, in my opinion, but Harden is right there in the mix, a member of a very small group.
This made me do some Googling and I found a pretty astounding stat: The NBA/ABA career leader for lowest turnover percentage is none other than... Ryan Freakin' Anderson Who would've thought? I could have made 500-1000 guesses before I got to his name.