In the 10 months since the New York Public Library announced plans for a $300 million renovation of its Fifth Avenue flagship building, scholars and writers have accused the library of abandoning its commitment to research and questioned how the circulating library across the street could be shoehorned into a treasured landmark.

But something crucial has been missing from this debate: what the transformed library will actually look like. On Wednesday, that will become clear when the library unveils the design by the British architect Norman Foster. Using space at the back of the building now occupied by seven floors of stacks, Mr. Foster has essentially created a major new contemporary library within Carrère & Hastings’s neo-Classical one.

The plans call for opening the building’s central axis from the Fifth Avenue entrance through to the Bryant Park side, where there will be a four-level atrium, with bookshelves, sitting areas and desks, that will replace the stacks space, which is now closed to the public. For the first time since the library was completed in 1911, patrons will be able to view Bryant Park through the tall, narrow windows on the ground floor.