LOVED IT! I finished Anathem by Neal Stephenson on audio today. This is some long, dense sci-fi that I really enjoyed. Lots of philosophy too.
Erasmus is a member of the Avout, a cloistered group that avoids the gadgets (called geegaws) and drugs of the secular world and devotes itself to learning. On this world, this group has been separate for thousands of years, gaining new members with infants being left with them or intelligent children joining. Erasmus is a Tenner, meaning he only gets to visit the outside world once every ten years for about two weeks. There are Hundreders and even Thousanders, though few people know much about the last group.
The story begins with Erasmus' first outing in 10 years, since he joined at about age 9. Things are Happening, and for a while we don't really know where the plot is going to go. Stephenson gives you several chapters to get used to this world and its vocabulary and technology, so that by the time stuff really gets going you can follow well without getting lost (much anyway). We find out that the secular power and the Avout have both discovered that an alien ship is orbiting the planted and the bulk of the story is dealling with who the aliens are and what they want.
But i really think the story is there to make people think about deeper philisophical concepts and the sort of person you want to be. I think the book is quite good, a 7.