Here's another good piece by Leon Neyfakh in Slate, an interview with William Rhodes.
The basic gist is this. Some people recidivate a lot while others do not at all. So if you look at everybody released from prison this year, indeed, two-thirds will be back (75 percent in five years). But if you look at individual people who have been to prison, most never come back! That's the interesting part, conceptually.
Here's the bottom line:
Two of every three offenders (68 percent) never return to prison. Another 20 percent return just once. The NCRP data are not definitive but it appears that most of these one-time returns are for violating the technical conditions governing community supervision rather than for new crimes. Importantly, only one in ten offenders (11 percent) returns to prison multiple times.