I read the book and thought it was terrific. The plot is great -- Robert Langdon is cute (he should have been blond) and the Sophie defnitely a french bombshell with a brain in between.
The references and the conversations in the book are out of the world and almost believable enough to make you mad (if you still believe in GOD as a person, object, diety whatever the holy guys do to make money).
It’s quite obvious no movie will be able to capture the essence of the book which itself is quite thick and takes time to read (in solitude). You need to struggle with the book a bit. By the time, one concept is dealt with - another comes up which defies your concentration at times.
Sophie is supposed to be internally hot and outwardly cool. Dosen’t look like it in the trailers. Tom Hanks seems to be miscast. He’s too old for running around a la Dev Anand.
My advice - READ THE BOOK FIRST.