Well, I hate to phone it in, but I have tried and failed to write one a few times now. So I've let someone else write one for me. Take as much or as little of this as you think is worthy of "elevator pitch"; any one paragraph will do but the most condensed for your intentions would probably be the third.

The Broken Earth is set on an Earth-like planet that is constantly subjected to large-scale seismic and volcanic events. The people of this land, which is called the Stillness, live in constant fear that an Angry Father Earth will unleash an environmental disaster strong enough to trigger a Fifth Season, a prolonged winter of hardship that can last anywhere from a decade to thousands of years. The Broken Earth is a resonant and cautionary work of climate fiction at a time when hurricanes, floods, and wildfires are pummeling the globe. Disaster preparedness is the organizing principle for people of the Stillness; they build for survival among the technological remains (the “deadciv”) of a long-dead civilization, which includes large mysterious obelisks that hover above them in the sky.

Among the people of the Stillness are orogenes, people born with the ability to harness and control kinetic, thermal, and other forms of energy. They alone can quell the seismic and volcanic events that threaten the Stillness. But orogeny is illegal, and orogenes (referred to as the derogatory term “roggas” by most people in the Stillness) are regarded as less than human. Orogenes are hunted down throughout the Stillness; those that aren’t killed are enslaved by the secret order of Guardians. Even more powerful than orogenes or Guardians are stone-eaters, a humanoid species that resembles stone statues and that rarely interacts with other beings in the Stillness.

Jemisin’s series centers on the story of Essun, a 42-year-old village schoolteacher who has been hiding her identity as an orogene. The Fifth Season begins with the shattering of two worlds: Essun’s husband discovers that their children are orogenes, kills the youngest, and kidnaps their daughter Nassun; the Stillness experiences an earthquake so powerful that it triggers the worst Fifth Season the planet has ever experienced. Jemisin immerses readers in the world of the Stillness: the journey that Essun sets off on to find her daughter propels the narrative, but Jemisin tells the story through multiple points of view and from multiple points in time. It’s an ambitious task to balance complicated world-building, a well-paced plot, and a range of fully distinctive characters, let alone to do so over the course of three novels. Jemisin deftly keeps all the plates spinning.