Interesting plot, but not a well-crafted story. The exact same events would’ve happened even if Robert Langdon didn’t exist. (Like Indiana Jones). Lots of head-hopping. Clumsy dialog. Not great at writing women either (or “woman”, since there was only 1).
The subjects matter saved this for me- the secret clues around Rome, the palindrome brands, the plots buried within other plots kept me guessing until the end.