One of the best things about Neal Stephenson’s works is that they make me feel just a bit smarter than I probably am. He gets into some pretty heavy mathematical, physics and philosophical areas but he holds your hand through them, explaining in a not too convoluted way. The novels can be enjoyed on a variety of levels, including a traditional adventure or mystery, but if you are willing to do a little work, you can get much more out of them. In my mind Stephenson is a stepping stone between Dan Brown and Umberto Eco.
Anathem introduces us to a world not much unlike our own except for monk-like orders of philosophers who live in varying degrees of isolation from the outside world. Much of the first third of the book is just setting this stage. Stephenson goes to great lengths to make this a fully realized world including a use of vocabulary on par with the Nadsat of A Clockwork Orange.
The central mystery revolves around an artificial object in the sky and what its implications are for the nature of reality, causality and Platonic ideals. We follow a young member of the order as he tries to understand why his mentor was kicked out of the order and why the outside government has summoned him, his friends and top intellectuals out of seclusion.
Another great read by Stephenson if a bit slow at the start, but if you are willing to do the work there is a payoff as everything starts to come together.