Unabashedly self-aggrandising and baldly longwinded, Ayn Rand's fourth and last novel is nevertheless a modern classic. Not without reason—as the clearest fictional account of her Objectivist philosophy (essentially right-wing economics mashed up with materialism and a merit-based social hierarchy), Atlas Shrugged is one of the most artistic philosophical novels of the 20th century. The opening question, "Who is John Galt?", despite having become ignominiously relegated to hipster bumper stickers of late, is nonetheless a genuine demand for an answer to the question of why society is in such disarray and what can be done about it.
The narrative centers on Dagny Taggart and Hank Rearden, lovers and metal-trade business executives. They support market economy in a dystopian future America being swallowed by socialism. The population is homogeneous, economic conditions are in decline, and the government gains more and more control by manipulating its citizens. John Galt symbolizes idealized individuality on one hand, and the public's resignation to worsening conditions on the other. Described by Rand as a mystery novel about the murder of man's spirit, Atlas Shrugged is philosophy posing as science fiction posing as social commentary.
This is a very long book. If you're looking for an introduction to Rand's basic ideas, Anthem is her shortest and most accessible work, though also the most intellectually immature. Sometimes you just need space to say what you want. The celebration of the human spirit and of individuality and ingenuity in Atlas Shrugged are refreshing against the generally bleak backdrop of 20th century literature, as is the "pure love" of Taggart and Rearden. If you want to be educated in modern novels you need to read Ayn Rand; if you really want to understand Ayn Rand, you need to read Atlas Shrugged.