Jean-Jacques Rousseau's book, The Social Contract, was first and foremost a politico-philosophical book describing what Rousseau believed to be the best form of government and society. One of Rousseau's main themes, linked very heavily with philosophies during the romantic era, was that society ought to return to a state that more closely resembled the state of nature. Rousseau believed that no one man should have the power to rule, but that by living in close proximity, individuals should govern themselves according to their own rules and laws that have been agreed upon. The points in this book were focused on a direct democracy: one that was run by the entire population (including women, which was a very radical suggestion at that point in time), and one that included small city-states where the government was entirely separate from the actual sovereign (the people). Many of these points were very influencial in social reforms in Europe, including the French Revolution. These ideas also influenced later philosophers like Immanuel Kant and Karl Marx.
Source: https://plato.stanford.edu/entries/rousseau/#PrinWorkRous