Radziwill's deal is reportedly worth $700,000 for a novel and a collection of essays, according to Page Six.
The journalist's first project for Henry Colt & Co is a fictional tale called The Widow's Guide to Sex & Dating, while the second book collects articles under the title Girl's Guide to Life.
Radziwill has confirmed that she recently signed a publishing deal, but declined to issue any further comment.
She worked as a producer for ABC News prior to her fame and also penned the bestselling autobiography What Remains: A Memoir of Fate, Friendship and Love.
The star joined The Real Housewives of New York City in the fifth season.