Larry Niven may be America's greatest living hard-SF writer. Much of his SF belongs to his famous future history, the Tales of Known Space. His preeminent creation is the Ringworld: an immense, artificial, ring-shaped planet that circles a Known Space star. Possibly SF's greatest feat of world-building, the Ringworld is featured in four novels: the Hugo and Nebula Award winner Ringworld (1970); The Ringworld Engineers (1980); The Ringworld Throne (1996); and Ringworld's Children (2004). Ringworld's Children returns series protagonist Louis Wu to the titular world. Louis and his friend The Hindmost, an alien of the Pierson's puppeteer race, are prisoners of the Ghoul protector Tunesmith, a Ringworld native, who is deliberately provoking the warships that surround his world. All the star-faring races of Known Space have sent warships to the Ringworld, and they are already at the brink of war. If fighting breaks out, the near-indestructible Ringworld will be destroyed: dissolved by antimatter weapons. The Ringworld series is so complex and ambitious that Ringworld's Children opens with a glossary and a cast of characters, inclusions that even many Known Space fans will need. Newcomers to Niven's artificial planet should start with Ringworld. --Cynthia Ward