Dan Brown has to be one of the most financially successful authors in
America today.

What are the gross sales of his four novels to date? How much is he
likely to have made in royalties on those sales? How much has he made
in ancilliary sales like movie deals? How much did he earn from all
these sources last year alone?

I am really interested in an accurate answer to the question,
especially regarding the gross sales of all Dan Brown novels.