Exordia by Seth Dickinson

“Anna sees an alien casually dining in Central Park’s Turtle Pond. On a lark, she confronts the alien and thus begins a relationship, and soon an NSA operative and his lifelong colleague in quasilegal intrigues take her back to her birthplace in Tawakul, Kurdistan. The Exordia have set off electromagnetic pulses (EMPs) all over Earth, taking most of the world back to the eighteenth century. But humanity isn’t entirely helpless. Canadians were the first to reach the site of a huge alien artifact that the Exordia wish to claim or destroy. Then the Ugandans arrived, then the Chinese, and Russians, and each group suffered losses. When the Americans arrive, they join forces with the remnants, but by bringing Anna, they’ve brought her renegade Exordian friend. Another alien operative is also on the ground, opposed to Anna. Now, the humans have 14 hours to activate the artifact or the Exordia battlecruiser will start nuking cities. Dickinson brings the same richness of characterization that made his Baru Cormorant series (The Traitor Baru Cormorant, 2015) so compelling, but this one reads like a Michael Crichton thriller on psychedelics—in a good way.” — Booklist, Starred Review