| Nick | Adriano | A security consultant. |
| Dr. Edwin H. | Anderson | The library's director. |
| John | Ashbery | An American poet and art critic. |
| Professor | Ashton | A college mentor. |
| Fred | Astaire | An American actor, dancer, singer, choreographer. |
| John Jacob | Astor | One of the founders of the library. |
| Leo | Astor | A stone lion. |
| Jane | Austen | An English novelist. |
| Mr. | Babenko | A longtime employee at the library. |
| Dr. | Bell | Harry's physician. |
| Alva | Belmont | One of the leaders of the New York suffrage movement. |
| Mr. | Benson | The janitor. |
| Albert | Berg | One of the donors of library manuscripts. |
| Henry | Berg | One of the donors of library manuscripts. |
| Joan | Blaeu | A Dutch cartographer. |
| Mr. | Blount | Claude's acquaintance. |
| Charlotte | Bronte | An English novelist and poet. |
| John Merven | Carrere | One of the building's architect. |
| Kate | Chopin | An American author of short stories and novels. |
| Inspector | Clouseau | Berg Collection's inspector. |
| Joseph G. | Cogswell | The first superintendent of Astor Library. |
| Charles | Dickens | An English writer and social critic. |
| Mabel | Dodge | Amelia's acquaintance. |
| Sadie | Donovan | The assistant curator. |
| Abigail | Duckworth | An author. |
| Max | Eastman | An American writer on literature, philosophy and society. |
| Elaine | Edmundson | The name used by Sadie when buying the lost books. |
| Elizabeth G. | Flynn | One of the members of the Heterodoxy Club. |
| Edwin | Gaillard | The library detective. |
| Inez Haynes | Gillmore | One of the members of the Heterodoxy Club. |
| Emma | Goldman | One of the members of the Heterodoxy Club. |
| Cary | Grant | An English-American actor. |
| Alexander | Hamilton | Founding Father of the United States. |
| Thomas | Hastings | One of the building's architect. |
| Nathaniel | Hawthorne | An American novelist, dark romantic, and a short story writer. |
| Dr. Humphrey | Hooper | The director of the library. |
| Marie Jenney | Howe | A feminist organizer and writer. |
| Washington | Irving | An American short-story writer, essayist, biographer, and historian. |
| Thomas | Jefferson | 3rd U.S. President. |
| Marlene | Jerkinson | Berg's curator and Sadie's mentor. |
| Richard | Jones-Ebbing | One of the new board members. |
| Jack | Kerouac | An American novelist. |
| | Kiernan | A judge. |
| Larry | Kline | The former mayor of Hawkins. |
| Fiorello | La Guardia | Former Mayor of New York City. |
| Robin | Larkin | A baby sitter. |
| James | Lennox | One of the founders of the library. |
| Leo | Lennox | A stone lion. |
| Jack | Lyons | The superintendent of the New York Public Library. |
| Laura | Lyons | Jack Lyons' wife. |
| Mrs. | Marino | One of the mothers at tenement. |
| Vladimir | Nabokov | A Russian-American novelist, poet, translator and entomologist. |
| Red | Paddy | Harry's acquaintance. |
| Dorothy | Parker | An American poet, writer, critic, and satirist. |
| Edgar Allan | Poe | An American writer, poet, editor, and literary critic. |
| Dr. Amelia | Potter | Worked from the city as medical inspector. |
| Joseph | Pulitzer | A newspaper publisher. |
| Hilary | Quinn | Laura Lyon's former secretary and executor in London. |
| Claude | Racine | Sadie's colleague. |
| Gretchen | Reynolds | One of Laura's classmates at Columbian Journalism School. |
| Auguste | Rodin | A French sculptor. |
| Margaret | Sanger | One of the members of the Heterodoxy Club. |
| William | Shakespeare | An English playwright, poet, and actor. |
| Mr. | Smith | One of the new board members. |
| Mrs. | Smith | One of the new board members. |
| Lesley | Stahl | An American journalist. |
| Alfred | Stieglitz | American photographer. |
| Frank | Tannenbaum | An Austrian-American historian, sociologist and criminologist. |
| Alfred | Tennyson | A British poet. |
| Bal | Thackeray | An Indian politician. |
| George | Wakeman | A professor at the Columbian University School of Journalism. |
| George | Washington | 1st U.S. President. |
| Wendy | Wasserstein | An American playwright. |
| Walt | Whitman | An American poet, essayist, and journalist. |
| Talcott | Williams | The head of Columbian Journalism School. |
| Virginia | Woolf | An English writer. |
| William Butler | Yeats | An Irish poet. |
| Beatrice | | Supposed name of Pearl. |
| Billy | | Jack Lyons' friend. |
| Bob | | A cat. |
| Chuck | | The owner of J&M Books. |
| Don | | Pearl's second husband. |
| Florence | | One of the members of the Heterodoxy Club. |
| Harry | | Jack and Laura's son. |
| Henrietta | | Amelia's acquaintance. |
| Ida | | Max Eastman's wife. |
| Jessie | | Amelia's partner. |
| Leonard | | Canadian singer-songwriter. |
| Lonnie | | Sadie's brother. |
| LuAnn | | Lonnie's wife. |
| Max | | A dog. |
| Pearl | | Jack and Laura's daughter. |
| Phillip | | Sadie's ex-husband. |
| Sam | | Harry's classmate. |
| Sarah | | Pearl's friend. |
| Sebastian | | Nick's dog. |
| Sue | | Nick Adriano's wife. |
| Valentina | | Sade's niece. |
