After college, while working with Thomason on their first novel, Caldwell worked at
MicroStrategy in
Tyson Corner and taught test preparation for
Kaplan, Inc. in
Blacksburg. Caldwell is married to his wife, Meredith, who earned her
DVM at
Virginia Tech. The couple lived in
Newport News, Virginia, before moving to
Vienna, Virginia. The couple has three children, Ethan, Jude, and Luke. Upon graduating from their respective colleges, Caldwell began working with Thomason on the novel
The Rule of Four. After writing together for a summer, the two continued to collaborate online and by telephone for the next five years. The plot centers on four Princeton seniors attempting to solve a mystery related to the
Hypnerotomachia Poliphili, an Italian work from the early
Renaissance. The book was published by
Dial Press in 2004, spent 49 weeks on
The New York Times Best Seller list and has sold almost 2 million copies. It was often compared to
Dan Brown's novel
The Da Vinci Code due to its similar style of teaching history through a fictional plot as well as the proximity in date of publication. It took Caldwell ten years to complete his second work,
The Fifth Gospel, which was published by
Simon & Schuster in 2015. This solo work tells the fictional story of two brothers, both priests, exploring the
Diatessaron, the "fifth" gospel, and how it might lead to reconciliation between the
Roman Catholic and
Eastern Orthodox churches. ==References==