I read it, when I was on painkillers and literally could not get out of bed.
I thought it was crap. The concept is fun and interesting, but the means by which the characters interact, escape from, and reunite with each other are ridiculously improbable.
One bit of action that set me on edge can be distilled down to: "Crap, we have to get out of France, but every cop in the country is looking for us. If we only had a private jet...oh wait, we do!"
There's alot of stuff like that. It read like a film script. Which, as it happens, it sort of was.
What blew my mind though was that Dan Brown actually believed that what he wrote as fiction was indeed true. It was an eye opener to the KOOK factor that I was unaware of before reading it.