I had it slighty worse: As a teenager I bought Holy Blood, Holy Grail on a whim (it were the 90s) in a bookstore because I was reading another Grail-focussed book series. HBHG is an utterly absurd book which could not even hoodwink a 14-year-old. One of the few books I deeply regret buying. Slightly later I read Focault’s Pendulum which of course inoculates one even more against this crap.
But of course Brown copied everything in his Da Vinci Code from HBHG which is obvious, when reading it. Every twist and turn is then utterly predictable. There was a copyright case in the 90s, annoyingly decided in Brown’s favour.
The real history behind HBHG is far more funnier: turns out the authors took their story from a french con-artist who fabricated documents and genealogies and deposited them into the Bibliotheque Francaise. And of course according the the con-artist the last descendant of the Merovingian Kings was himself.