From my family and friends who read/liked Dan Brown and/or Clive Cussler (and/or Twilight, 50 Shades, and countless others) footnote
From my friends who only read based on the NYT Best Sellers list:
From my friends in the publishing industry:
(I take NO credit for the originality of this post or the gifs contained herein. Please see here for the original I have shamelessly ripped).