Some of Nora Roberts' popular trilogies are the "Concannon Sisters Trilogy" and the "Key Trilogy." Another popular trilogy with supernatural themes is the "Sign of Seven Trilogy."
The "Concannon Sisters Trilogy" follows three sisters from Ireland. "Born in Fire" focuses on Maggie Concannon, who creates beautiful art pieces made from glass. Rogan Sweeney is determined to help her build a profitable career. "Born in Ice" focuses on Brianna when a famous American writer spends the winter at her bed-and-breakfast. "Born in Shame" follows Shannon Bodine, a prominent advertising agent, and how she learns her real father is Thomas Concannon.
The "Key Trilogy" is about Malory, Dana and Zoe, who are in a financial rut until they attend a mysterious dinner party. "Key of Light" follows Malory, who loses her job to her boss' new wife but is sent on a quest for a key. In the process she meets an editor for the local newspaper. In "Key of Knowledge," Dana searches for a key as she renovates the new business she hopes to open. "Key of Valor" follows Zoe as she searches for her key while fighting against a sorcerer named Kane.
"Blood Brothers," the first of the "Sign of Seven Trilogy," follows three best friends who unknowingly unleash a 300-year curse. "The Hollow" describes the consequences that accompany releasing the curse, and how the friends prepare to fight them. "Pagan Stone" focuses on the battle between the friends and the demon attached to the curse, who keeps getting stronger.