In Jerusalem, a gleaming white dome and a black basalt wall shield Israel's greatest treasures—not bejeweled crowns or scepters but unadorned texts. Visitors to the Shrine of the Book, a wing of the Israel Museum, can descend a steep flight of stairs from the main hall, where the Dead Sea Scrolls are on display, and arrive at a small chamber that houses the oldest and most authoritative copy of the Hebrew Bible.

Or so it appears. In fact, the full Aleppo Codex, as the copy is called—a bound volume of vellum pages also known as the Crown of Aleppo—is stored in a nearby vault. Only its topmost leaf, the one that viewers see, is from the codex itself. The rest is a dummy, cleverly arranged by the curators to appear real. As Matti Friedman observes in "The...