I haven't read Ludlum in about 15 years. He was one of the first authors that I read extensively. Clancy as well, I read all of his earlier books, but haven't lifted one of those suckers at half a dozen years. I used to read a lot of the Spy/Thriller fiction genre of books.
More recently I've been spending my time reading Scientific/Mathematics books.
Presently, I am reading "Galileo's Daughter" by Dava Sobel, which is an absolutely fantastic book. Sobel also wrote "Longitude", which is one of the best books I've ever had the pleasure to read.
