The Lost Symbol is a thriller novel by the renowned author Dan Brown, published in 2009. It is the third novel in the Robert Langdon series and follows the story of Langdon as he is called to give a lecture at the United States Capitol Building but becomes embroiled in a dangerous search for the legendary Masonic pyramid.

The novel is set in Washington D.C., and follows Langdon as he teams up with Katherine Solomon, a scientist and the sister of his mentor, to uncover the secrets of the pyramid and its connection to the ancient mystical practices of the Masonic order. Along the way, they must navigate a complex web of clues and symbols, while being pursued by a shadowy organization known as the Ancient Mysteries.

One of the strengths of The Lost Symbol is its attention to detail and historical accuracy. Brown weaves a complex tapestry of Masonic history and symbolism throughout the story, drawing on real-world locations and events to create a sense of authenticity. Brown also touches on themes of spirituality and faith, as well as the conflict between science and religion, adding depth to the story and giving readers plenty to ponder.

Another strength of the novel is its pacing. Brown is a master of suspense and The Lost Symbol is no exception. The novel moves at a breakneck pace, with twists and turns that keep the reader on their toes. The characters are also well-developed, with Langdon and Solomon both serving as strong protagonists. The secondary characters, including the villains, are also well-drawn and add depth to the story.

One of the most intriguing aspects of The Lost Symbol is its exploration of the Masonic order. Brown delves into the history and practices of the organization, drawing on real-world sources to create a sense of authenticity. While some of the more sensationalist aspects of the story may be contested by Masonic scholars, Brown's portrayal of the organization is generally considered respectful and well-researched.

Overall, The Lost Symbol is a thrilling and thought-provoking novel that showcases Brown's skill at weaving intricate plots and drawing on real-world history and mythology. The novel's success led to a film adaptation being planned, though it was ultimately cancelled. For fans of the genre or those interested in the Masonic order and its history, The Lost Symbol is a must-read.