Rameau's Nephew is wonderful. It's witty and funny, and except for a few incidental details, feels like a contemporary conversation. I was less enamored of D'Alembert's Dream, but it could be interesting from a history of science point of view. Still, I'm impressed by Diderot's range. What really comes through most of all is Diderot's personality, especially his intellectual curiosity and playfulness. He's now at the top of my "who would you have dinner with" list (not that I keep a list like that, but sometimes people ask that kind of thing).