This country,” writes Bill Keller in What’s Prison For?: Punishment and Rehabilitation in the Age of Mass Incarceration, “imprisons more people more copiously than almost any other place on earth.” This reality has led to “a growing consensus that we lock up too many people for too long.” Keller is a former executive editor of The New York Times and the founding editor-in-chief of the Marshall Project, a nonprofit news organization that covers criminal justice in the United States. His slim, readable volume is one of the latest additions to the burgeoning literature decrying “mass incarceration” in the United States.

The author wastes no time in telling the reader what should be done about this state of affairs: decriminalize such minor crimes as “low-level drug offenses”; divert some criminals to “mental health and addiction programs, or probation or community service”; “abolish mandatory minimum sentences and encourage prosecutors and judges to apply the least severe punishment appropriate under the circumstances”; “raise the age at which accused youngsters are subject to adult punishment”; “give compassionate release to old and infirm inmates”; and “reduce the use of cash bail.” The evidence of recent years, he claims, demonstrates that states “can cut prison populations without jeopardizing safety.”