Nearly eight years have passed since Robert Langdon, the world's most dashing tenured faculty, found himself ensnared in a dangerous global conspiracy. That's a long wait for the professor's loyal readers — but his spell of peace and quiet (and peer-reviewed research, presumably) is at an end. With the publication of The Secret of Secrets — Dan Brown's sixth installment in a saga that includes The Da Vinci Code — this week welcomes the return of an astonishingly popular series that has sold untold millions, spawned three Tom Hanks blockbusters and occasionally stoked controversy with its greatest hits list of...