If science fiction is a genre that asks “what if?”, then the authors of these five books have really outdone themselves. These are novels that go beyond the ordinary to ideas so outlandish that lesser authors might have rejected them as too insane. But these books aren’t comedies. These aren’t the kind of oddball concepts that just devolve into nonsense. Instead, these books take their audacious premises seriously, and bit by bit, explore the consequences to the characters and to humanity at large.

Darwinia, Robert Charles Wilson

Europe disappears. It’s there one day in 1912, and gone the next. The land itself doesn’t vanish, but ships trying to arrive in port discover an untamed and unnatural wilderness where the continent once stood. Out of fuel, the ships are stranded there with no easy way back. And the millions of people who used to live there? Gone.

The Flicker Men, Ted Kosmatka

There’s a common misconception about quantum physics that reality doesn’t actually exist until it is observed. It’s the stuff of quack pseudoscience, but Kosmatka uses it as his premise: If this were really true, then what would we find when we studied the phenomenon? Would all humans be able to collapse the wave? What about animals? Children? The unborn? It’s a simple premise that kicks off a whirlwind of implications and follows them to far-reaching conclusions.

The Three-Body Problem, Cixin Liu (translated by Ken Liu)

Since this book just won the Hugo Award, nobody needs me to tell them about it! It has lots of ideas, but the one audacious one that caught my attention: A character begins to see a countdown in every photograph he takes (but not in the photos his wife takes with the same camera). A countdown to what? That’s the question.

The Chronoliths, Robert Charles Wilson

I didn’t want to repeat an author in this list, but Wilson is practically the king of audacious premises. (His novel Spin could easily make the list as well.) In this book, a huge monolith suddenly appears in Asia commemorating the victory of an unknown leader in a battle to take place 30 years in the future. Was it sent back in time? Will it really happen? Is it a hoax? Then a second monolith appears, mapping further conquests. And a third…

The Time Traveler’s Wife, Audrey Niffenegger

A man has a unique ailment: He travels in time. Uncontrollably. Frequently. Without warning, he jumps to some place and time important to him, frequently meeting his wife before he actually met her. It creates an incredible skein of mismatched cause-and-effect as he and his wife experience the major events in their relationship in a different order from each other. And incredibly, it all ties together perfectly.

Novels like these are some of the most exciting things science fiction can offer: ideas that no other genre can match. Ideas that are not only creative, but that dig deeper, delving into how the world around us works, and what makes us human.

David Walton is the Philip K. Dick Award-winning author of the 2015 quantum physics thrillers Superposition and Supersymmetry, a pair of books with audacious ideas of their own. You can read more about his work at his website.