Initially, the group was an informal gathering of friends who met with Rand at her apartment on weekends to discuss philosophy. Later, Rand began allowing them to read the manuscript drafts of her new novel, Atlas Shrugged. In 1954, her close relationship with Nathaniel Branden turned into a romantic affair, with the knowledge of their spouses. Published in 1957, Atlas Shrugged is considered Rand's magnum opus. She described the novel's theme as "the role of the mind in man's existence—and, as a corollary, the demonstration of a new moral philosophy: the morality of rational self-interest". It advocates the core tenets of Rand's philosophy of Objectivism and expresses her concept of human achievement. The plot involves a dystopian United States in which the most creative industrialists, scientists, and artists respond to a welfare state government by going on strike and retreating to a hidden valley where they build an independent free economy. The novel's hero and leader of the strike, John Galt, describes it as stopping "the motor of the world" by withdrawing the minds of the individuals contributing most to the nation's wealth and achievements. The novel contains an exposition of Objectivism in a lengthy monologue delivered by Galt. Despite many negative reviews, Atlas Shrugged became an international bestseller, but the reaction of intellectuals to the novel discouraged and depressed Rand. Atlas Shrugged was her last completed work of fiction, marking the end of her career as a novelist and the beginning of her role as a popular philosopher. In 1958, Nathaniel Branden established the Nathaniel Branden Lectures, later incorporated as the Nathaniel Branden Institute (NBI), to promote Rand's philosophy through public lectures. He and Rand co-founded The Objectivist Newsletter (later renamed The Objectivist) in 1962 to circulate articles about her ideas; she later republished some of these articles in book form. Rand was unimpressed by many of the NBI students and held them to strict standards, sometimes reacting coldly or angrily to those who disagreed with her. Critics, including some former NBI students and Branden himself, later described the culture of the NBI as one of intellectual conformity and excessive reverence for Rand. Some described the NBI or the Objectivist movement as a cult or religion. Rand expressed opinions on a wide range of topics, from literature and music to sexuality and facial hair. Some of her followers mimicked her preferences, wearing clothes to match characters from her novels