Renzo Piano’s Morgan Library extension is a major addition, writes Nicolai Ouroussoff. “A sublime expression of the architect’s preoccupation with light, the design transforms the world of robber barons and dust-coated scholars conjured by the old Morgan into a taut architectural composition bursting with civic hope. His triumph at the site, where order is brought to a jumble of buildings collected over nearly a century, should temporarily allay complaints that New York’s cultural institutions shrink from a high level of architectural innovation.”