The Lost Symbol

The Solomon Key is the working title of an unreleased novel in progress by American author Dan Brown.
The Solomon Key will be the third book involving the character of the Harvard professor Robert Langdon, of which the first two were Angels & Demons (2000) and The Da Vinci Code (2003). According to early reports, the book's story will take place in the Washington, D.C. area, and focus on the work of the Freemasons.
The book has been in development for several years and the projected publication date has been pushed back multiple times. As of early 2009, no firm release date has been announced.
On February 12, 2009, Ron Howard reported to ETonline from the movie set of Angels and Demons that Brown had completed The Solomon Key.