I would consider this anthology an essential read for those who are even mildly interested in progressive/leftist schools of thought. Not every writer in here is socialist/communist (in fact I would argue that the majority are not) but each writer has a common goal of resisting oppression of the ruling class.
Whether it is the tiny island of Melos asking for autonomy from Ancient Athens, or Russian serfs rising up against their tsars, history cannot erase the fact that these people fought for themselves and the writings in this book are proof of that.
Highlights for me include "Law and Authority" by Peter Kropotkin, "The Quest for the Golden Fleece" by W.E.B. Dubois, "The Ballot or the Bullet" by Malcolm X, and "Violence and Love" by R.D. Laing.