The story of "Lexicon" is an unusual one. To quote Barry himself from his own site, the story is centered around "a secret persuasion society that builds and deploys words as weapons." The protagonist is a woman who is recruited into the society's ranks, but makes the mistake of breaking the cardinal rule of falling in love. Vaughn plans to adapt the novel himself, but will likely bring frequent collaborator Jane Goldman into the process at some point.
Of course, Vaughn didn't just stumble upon "Lexicon" -- the novel won't be released until next year. Deadline reports that Barry’s agents sent a copy of the book to Vaughn, which prompted him to purchase the film rights.
Don't expect "Lexicon" any time soon. With Vaughn starting production on the 'First Class' sequel in early 2013, it's doubtful that he'll be ready to move onto another project for a while. Furthermore, should Millar get in his ear, there's a chance that one of his projects will move up on Vaughn's production slate before "Lexicon."