Richard V. Reeves’s new book, “Of Boys and Men,” is a landmark, one of the most important books of the year, not only because it is a comprehensive look at the male crisis, but also because it searches for the roots of that crisis and offers solutions.

I learned a lot I didn’t know. First, boys are much more hindered by challenging environments than girls. Girls in poor neighborhoods and unstable families may be able to climb their way out. Boys are less likely to do so. In Canada, boys born into the poorest households are twice as likely to remain poor as their female counterparts. In American schools, boys’ academic performance is more influenced by family background than girls’ performance. Boys raised by single parents have lower rates of college enrollment than girls raised by single parents.

Second, policies and programs designed to promote social mobility often work for women, but not men. Reeves, a scholar at the Brookings Institution, visited Kalamazoo, Mich., where, thanks to a donor, high school graduates get to go to many colleges in the state free. The program increased the number of women getting college degrees by 45 percent. The men’s graduation rates remained flat. Reeves lists a whole series of programs, from early childhood education to college support efforts, that produced impressive gains for women, but did not boost men.

Reeves has a series of policy proposals to address the crisis, the most controversial of which is redshirting boys — have them begin their schooling a year later than girls, because on average the prefrontal cortex and the cerebellum, which are involved in self-regulation, mature much earlier in girls than in boys.

There are many reasons men are struggling — for example, the decline in manufacturing jobs that put a high value on physical strength, and the rise of service sector jobs. But I was struck by the theme of demoralization that wafts through the book. Reeves talked to men in Kalamazoo about why women were leaping ahead. The men said that women are just more motivated, work harder, plan ahead better. Yet this is not a matter of individual responsibility. There is something in modern culture that is producing an aspiration gap.