The Lazarus Long set of books involve time travel, parallel dimensions, free love, individualism, and a concept that Heinlein named World as Myth—the theory that universes are created by the act of imagining them, such that even fictional worlds are real.
World Cup | FIFA World Cup | World Trade Center | World Series | 2010 FIFA World Cup | World Bank | World Health Organization | Guinness World Records | 1978 FIFA World Cup | World Series of Poker | Allies of World War II | BBC World Service | ATP World Tour 250 series | World Heritage Site | World Boxing Association | World Boxing Council | 2006 FIFA World Cup | World Wide Web | As the World Turns | World Trade Organization | ATP World Tour 250 Series | World Rally Championship | World Intellectual Property Organization | World Economic Forum | Western world | Miss World | Rugby World Cup | World Meteorological Organization | World Championship | The Real World |
It is the last of the "Lazarus Long" cycle of stories, involving time travel, parallel dimensions, free love, voluntary incest, and a concept that Heinlein named pantheistic solipsism, or World as Myth — the theory that universes are created by the act of imagining them, so that somewhere (for example) the Land of Oz is real.