I tend to dislike fiction where the author breaks the "fourth wall" by popping into the text to say something clever. Stephenson does this a lot in his books (the ones I've read), but I tend to make an exception for him. Nevertheless, I liked this book better than Snow Crash or The Diamond Age because it seems he does the "clever authorial injection" less in this book. Also the plot hangs together better. So my overall impression of the book was that it is more "mature" than those earlier works.
It has all the other stuff that Stephenson does well: multiple complex societies with long histories, with echoes of old Earth cultures, interacting in interesting ways; hard science, math, and philosophy explained in lay language (he did a particularly good job of explaining the science in this book; he did a less good job with the philosophy); plot twists and puzzles; multiple points of view.
Stephenson is less good at portraying romantic relationships, emotion, and complex character development than at that other stuff. The main characters do develop and most of the characters have distinct personalities and realistic, if simple relationships. It works well enough and doesn't distract from what he's good at.
I particularly enjoy a novel that makes up a society I want to live in, and Anathem does a great job of that. (I've always kind of wanted to live in a monastery, except for the celibacy and believing in religion parts.)
Another reviewer on Goodreads complained about all the made-up words in Anathem. I think this is one way in which the audio version is superior to the paper version. I knew that made-up words were being used, but a lot of them sound enough like Latin and French words that I didn't get very distracted by them.
The audiobook is narrated well, mainly by William Dufris. Stephenson himself reads some of the definitions from "The Dictionary, 4th Edition, A.R. 3000" that preface each chapter.
The audio production includes monastic-sounding vocal music that was composed for it; it includes overtone singing similar to that performed by the Gyuto monks. (You can hear more of it on the Neal Stephenson web site.)
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