Civil Disobedience is one of the most importance works of philosophy ever written. Like all great works of philosophy, it is as relevant today as it has ever been, as it transcends space and time. Don't let the abolitionist nature mislead you: this book is not merely about abolition and slavery. Rather, it is about Man Against the State, individuality, and Thoreau's philosophy of how one man can stand up to government and society, driven by his own convictions of right and wrong, as summarized by the timeless quote "Any man more right than his neighbors constitutes a majority of one already".
Thoreau's main point is that the best - and many times, the only - method for fighting injustice is through passive disobedience. By refusing to cooperate with the machinery of injustice, the individual can become the friction that stops the machine. Active resistance is bound for failure, as the machine (the State, society, etc.) is too formidable for the individual to fight. But, by refusing to cooperate, justice can be achieved and injustice toppled.
If you are looking for a marvelous primer on individuality and the fight for justice, start with this book.
