We've heard a lot in recent years about the nearly 2.1 million people incarcerated in American prisons and jails. But what about the approximately four million more who are on probation and parole—monitored by the state at great expense and at risk of being sent to prison at the whim of a probation or parole officer for the least imaginable infraction?

Vincent Schiraldi was New York City probation commissioner under Mayor Bloomberg, supervising a system charged with monitoring 30,000 people on a daily basis. In Mass Supervision, he combines firsthand experience with deep research on the inadequately explored practices of probation and parole, to illustrate how these forms of state supervision have strayed from their original goal of providing constructive and rehabilitative alternatives to prison. They have become instead, Schiraldi argues, a "recidivism trap" for people trying to lead productive lives in the wake of a criminal conviction.

Schiraldi offers the first full and up-to-date account of these two key aspects of our criminal justice system, showing that these practices increase incarceration, have little impact on crime rates, and needlessly disrupt countless lives. Ultimately, he argues that they should be dramatically downsized or even abolished completely.