This is what most people think of when they think of "science fiction". The future, technology, robots and invasions of Earth by little green men. But sometimes hard SF cuts so close to where we actually are that you have to look hard to see the twists that take it out of mainstream and into science fiction. One of the earliest practitioners was the French novelist, Jules Verne. His science was so hard and so tight he extrapolated much less than people think, on occasion. For example, his 'Nautilus' is often said to foreshadow "successful submarines" by pedants who do not realise it was named in honor of a working submersible of the Napoleonic period. He also established the formula that the science will be shown to the reader as the source, motivation, obstacle, and solution of an adventure story.

One sub-sub-genre of hard SF you might want to check is Cyberpunk. Another distinct genre we will look at but haven't broken out is military SF, as conquered by the likes of David Drake and Elizabeth Moon.

Where to start? There are literally thousands of SF titles. These are just a few to illustrate the breadth of the genre:

• The Enemy Stars by Poul Anderson
• I,Robot and The Gods Themselves by Isaac Asimov
• The Foundation Series by Isaac Asimov
• Darwin's Radio by Greg Bear
• Ender's Game by Orson Scott Card
• Heavy Time and Hellburner by C.J. Cherryh
• Downbelow Station, 40,000 in Gehenna, Cyteen, Merchanter's Luck, Rimrunners, Finity's End and Tripoint by C.J. Cherryh
• Do Androids Dream of Electric Sheep? by Philip K. Dick, inspiration for the movie Bladerunner and our candidate for the best title ever
• Hammer's Slammers, Volumes I, II, and III by David Drake
• The Forever War by Joe Haldeman
• The Moon is a Harsh Mistress and Starship Troopers by Robert Heinlein
• Dune, Dune Messiah, or Under Pressure by Frank Herbert
• A Spectre is Haunting Texas and The Wanderer by Fritz Leiber
• The Ship Who Sang by Anne McCaffrey
• Haze and Hammer of Darkness by L. E. Modesitt, Jr.
• The Vatta's War series by Elizabeth Moon: Command Decision, Engaging the Enemy, Marque and Reprisal, Victory Conditions
• Ringworld by Larry Niven
• Diving into the Wreck by Kristine Kathryn Rusch
• The Weapon Shops of Isher and The Weapon Makers by Fred Saberhagen
• Frankenstein by Mary Shelley. Even though this one is straight horror, it is also one of the first pure SF books ever written.
• Ilium by Dan Simmons
• Riding the Torch by Norman Spinrad
• The Blue World by Jack Vance
• From the Earth to the Moon and 20,000 Leagues Under the Sea by Jules Verne
• The Time Machine, The Island of Doctor Moreau, and Things to Come by H. G. Wells