As NASA's manned space efforts shrank, starships became more the stuff of science fiction. The following envision different paths to expansion into space.
Voyage, by Stephen Baxter (1996): An epic saga of America's might-have-been. If President John F. Kennedy had lived, we could have sent a manned mission to Mars in the 1980s.
Coyote, by Allen Steele (2002): Gallant misfits, led by a spaceship captain named Robert E. Lee, steal a starship. They flee a declining Earth rife with dictatorship and technophobia to found a new society on a new world.
Time for the Stars, by Robert A. Heinlein (1956): Identical twins are enlisted to be the human radios that will keep starships in contact with Earth, but one of them has to stay behind while the other explores the depths of space. Einstein intervenes.
Earth, by David Brin (1990): A small black hole escapes from the lab that made it, and Earth is in danger of being hollowed out. Wracked by gravity lasers from core to pole, Earth explores whether humanity and freedom can survive.
Hull Zero Three, by Greg Bear (2010): Interstellar planet hunting on an enormous damaged starship. Strange things have come to live in the starship's vast corridors on the long voyage.
The Highest Frontier, by Joan Slonczewski (2011): College in an orbital space habitat. Global climate change and advanced social change amid an intriguing biotech future.
A Fire Upon the Deep, by Vernor Vinge (1992): Supersmart entities rule part of our galaxy. Human minds remain limited, but our lot is not as bad as that of creatures in the Unthinking Depths, where only simple animals can function. Add conflicts and stir.
Mars Crossing, by Geoffrey A. Landis (2000): Adventurers endure an agonizing trek halfway across the surface of Mars to reach a ship designed to carry only half their number. A rugged, inventive tale.
Red Thunder, by John Varley (2003): A Chinese spacecraft, Heavenly Harmony, threatens to land on Mars a few days before the U.S. shuttle gets there. A tribute to Heinlein, the space program, and American ingenuity.
Red Mars, Green Mars, Blue Mars, by Kim Stanley Robinson (1992–1996): A trilogy about founding a Mars colony. The settlers fragment into political factions which differ on how to alter the Mars environment and govern the first society independent of Earth.