Creating a sense of grandeur while making the most efficient use of space was crucial to the renovation of this prewar duplex apartment on Manhattan’s Upper East Side. An intimate entry vestibule clad in marble with a crown of gold leaf and alabaster precedes the grand, double-height foyer where a helix-shaped staircase ascends to the second floor. Here the original two bedrooms and bathrooms were reconfigured to create a master suite complete with French doors leading to a library. Warmed by an oversized fireplace, deeply colored wooden plank flooring, and mahogany and steel bookshelves, the library recalls the Gothic reading rooms of university clubs. It is an inner sanctum for reflection and scholarship.