Wow, when Dan Brown finds a formula he likes, he digs his teeth into it and just doesn't let go!
Extended scavenger hunt through the secret past of a city? Check.
Attractive woman (often a scientist) who will tag along?
A villain with an obviously fake name who will end up being someone we've met before? Check.
A villain/henchman who is often noticeably physically different in appearance who will follow their beliefs/patron with zeal and fanaticism? Check
The death or mutilation of a powerful person requiring that Robert Langdon be called in? Check.
So how do you even rate The Lost Symbol, given that so much of it is a retread of his last two books? It's entertaining, fast-paced, and doesn't bear more than a moment's thought.
Oh, and the reveal about who the bad guy "really was?" Painfully telegraphed. I knew over half a book before it was revealed. And Brown tends to get off on making sure his characters know more than the reader, which is really false drama, in cases like this, where a couple of sentences could clear the whole damned thing up.
A beach read, a mindless read, but never anything more. And the formula is getting worn and creaky and showing signs of age.