Technically speaking, Dan Brown's Langdon books are part of a series in a common universe.
But at first glance, they don't seem to be all that related to each other - more like Fleming's 007 than Harry Potter.
Are you required to read any of Langdon books by Dan Brown to properly understand and enjoy the next ones?
If not, is there important information in any of the earlier books that the reader of later books would find necessary to increase their understanding/enjoyment (assuming they aren't afraid of spoilers)