THE FOLKS BEAVERING away in the magisterial Rose Main Reading Room at the New York Public Library might be excused for feeling spied upon. What is that thing? they keep asking the guards, pointing at the eerie, radarlike dish mounted on the balcony at the far end of the vaultlike space. Much of the time, the object is unmanned. But every so often, a lanky long-haired young man will squeeze himself into the narrow cockpit, wedging his skull into a white helmet, and start taking measurements, or inventories, or something. He is Trevor Oakes, who, along with his identical twin, Ryan, has been engaged since toddlerhood in a decades-long investigation into the nature of bifocal perception, the way that other identical twins might have evolved a hermetic secret language.
“When…