Her writing career evolved from her work as a writer of documentary and educational films. Her essays and opinion pieces have appeared in national newspapers including The New York Times and The Boston Globe, and on mass market magazines like House & Garden, Metropolitan Home, and Good Housekeeping. Upon publication of her first book, the memoir When I was Puerto Rican, Ms. Santiago was hailed as "a welcome new voice, full of passion and authority," by The Washington Post Book World. Her first novel, América's Dream, has been published in six languages, and was an Alternate Selection of the Literary Guild. "Thrilling and page turning, the fabulous story of América Gonzalez is laid out masterfully," according to the Chicago Tribune. Her second memoir, Almost a Woman, received numerous "Best of Year" mentions, in addition to an Alex Award from the American Library Association. It has recently been adapted into a film for Exxon Mobil Masterpiece Theatre, which premiered nationally on PBS on September 14, 2002. With Joie Davidow, Ms. Santiago is coeditor of the anthologies, Las Christmas: Favorite Latino Authors Share Their Holiday Memories and Las Mamis: Favorite Latino Authors Remember their Mothers both published by Knopf. Her 2004 memoir, The Turkish Lover, describes her life from the time she left New York at age 21 until her graduation from Harvard in 1976, and focuses on her relationship with Turkish filmmaker Ulvi Dogan. While still in high school, she was cast in a small role in the 1967 film version of Bel Kaufman's novel Up the Down Staircase, wherein she portrayed a student named Esmeralda. She spoke at the 2011 National Book Festival about her book Conquistadora, which she says will be a trilogy, saying her characters spoke and sang to her while she wrote the book. While researching the book she came to discover that she has African ancestry from the slaves that were bought to Puerto Rico.
Activism
In addition to her literary endeavors, Ms. Santiago is an active volunteer. She is a spokesperson on behalf of public libraries. She has designed and developed community-based programs for adolescents, and was a founder of a shelter for battered women and their children. She serves on the boards of organizations devoted to the arts and to literature, and speaks vehemently about the need to encourage and support the artistic development of young persons. Santiago often repeats that Puerto Ricans and other people who come to the United States were invisible before memoirs were written about them.
Stroke
In 2008, Santiago had a stroke affecting her ability to read and speak. After a long rehabilitation program, Santiago's recovery from stroke has been largely successful, though not complete. She estimates that today her reading ability in English is at about “98 percent,” and in her native Spanish about “80 percent,” in part because English has been her predominant language since coming to the U.S In 2011, three years after the stroke, she finished her epic novel, Conquistadora.