While sympathetic to Randal's point, I suspect he hasn't devoted quite enough attention span to get what Stephenson is actually up to in this one. It is the sort of book where putting it down too soon will make it impossible to pick up. Being set in an entirely distinct culture it requires a fair amount of context and vocabulary to keep the alien flavor. Although, if you are well-read in the right topics, a lot of what is said will sound isomorphic to things you already know.
Read in the right frame of mind, it might even teach some hard to explain ideas about the nature of consciousness. There is an interesting riff relating the solving of an abstract problem to the collapsing of a wave function, and a different spin on the many-worlds explanation of quantum mechanics that almost made sense.
As I write this, I've read about 3/4 of Anathem, and it clearly is worth the attention I've paid it.
As proof that XKCD does get it in general, I present the previous comic, which demonstrates the power of a log scale to collapse the entire universe to a comprehensible size...