I've been a fan of Umberto Eco for many years. I read The Name of the Rose (aside: a great list of SIPs for this book!) about 20 years ago while I was in college. It made for perfect summer reading. It was fine story-telling combined with amazing research and a fantastically imaginative intelligence.
I was also captivated by Foucault's Pendulum and The Island of the Day Before and a collection of essays called How to Travel With a Salmon and Other Essays. I still have Baudolino sitting in my pile of books to be read. And I know I'll have to run out and get The Mysterious Flame of Queen Loana very soon.
I loved Foucault's Pendulum. I read it twice (the first time with a dictionary and an encyclopedia next to me) and ate up the complicated plot and twisted conspiracy theories. I am one of those who thinks The Da Vinci Code was a poor (okay, awful) substitute for Eco's amazing look into secret societies.
The Telegraph has a wonderful profile of Eco (who, I was surprised to learn, is 73 years old!) where he muses about his reputation as the thinking person's writer and his surprise at his fame.
On a side note: am I the only one who thinks The Da Vinci Code was a horribly written book? Most reviews I've read gush about what a page-turner it was and how astounding the premise was. I had already read the premise in Foucault's Pendulum and I barely made it through the book with my husband nagging me through it (he loved it). He actually ends Chapter 64 with "And then everything went black." Gah!