For those unaware, Dorothy Day is sort of a proto-Red scare girl. She was a socialist activist who became a Catholic. Except, instead of becoming a lame, cringe-worthy reactionary, she actually managed to integrate Catholicism and socialism. Founding the Catholic Worker Movement in 1933, the organization seeks through charity, to build community without invalidating the individual. If you couldn't guess, she was big into the commune part of communism.

Her life could be the subject of an excellent biography (and there are probably a few out there), but that's not what this book is about. Rather, Dorothy uses her life as a pretext to explore the idea of "the long loneliness"—the urge that human beings have for one another, the eternal feeling of being incomplete. She posits that the solution to that problem is community.

As a result, the book is not really about her but rather about the people in her circle. She isn't writing this to define herself as an individual but to showcase how her relationships with others impacted her life. The book is actually an account of her perception of the people close to her. It's a biography, not of a single person but of the first half of the 20th century, the environment she grew up in, and the Catholic Worker Movement she helped create.

Anyways, TL;DR, I'd read it if I were you. It's good. In fact, this book just might be the writings of the next Catholic saint. She's only two miracles away, and if you asked me, that's close enough for our lifetimes.