Ada Sibelius is raised by David, her brilliant, eccentric, socially inept single father, who directs a computer science lab in 1980s-era Boston. Home-schooled, Ada accompanies David to work every day; by twelve, she is a painfully shy prodigy. The lab begins to gain acclaim at the same time that David’s mysterious history comes into question.

When his mind begins to falter, leaving Ada virtually an orphan, she is taken in by one of David’s colleagues. Soon she embarks on a mission to uncover her father’s secrets: a process that carries her from childhood to adulthood. What Ada discovers on her journey into a virtual universe will keep the reader riveted until The Unseen World’s heart-stopping, fascinating conclusion.

A Head Full of Ghosts is a chilling thriller that brilliantly blends psychological suspense and supernatural horror. The novel is reminiscent of Stephen King's The Shining, Shirley Jackson's The Haunting of Hill House, and William Peter Blatty's The Exorcist.

The lives of the Barretts, a normal suburban New England family, are torn apart when fourteen-year-old Marjorie begins to display signs of acute schizophrenia. To her parents' despair, the doctors are unable to stop Marjorie's descent into madness. As their stable home devolves into a house of horrors, they reluctantly turn to a local Catholic priest for help. Father Wanderly suggests an exorcism, believing the vulnerable teenager is the victim of demonic possession. He also contacts a production company that is eager to document the Barretts' plight for a reality television show.

With John, Marjorie's father, out of work for more than a year and the medical bills looming, the family agrees to be filmed, and soon find themselves the unwitting stars of The Possession, a hit reality television show. When events in the Barrett household explode in tragedy, the show and the shocking incidents it captures become the stuff of urban legend.

Fifteen years later, a bestselling writer interviews Marjorie's younger sister, Merry. As she recalls those long-ago events that took place when she was just eight years old, long-buried secrets and painful memories that clash with what was broadcast on television begin to surface. A mind-bending tale of psychological horror is unleashed, raising vexing questions about memory and reality, science and religion, and the very nature of evil.