Not a mystery.
There are 935 pages.
Fan is derived from fanatic.
Let's link these thoughts together.
Although Anathem turned out not to be a mystery, I may have liked the book. Then again, I may not have. Let's keep talking about it. There was a murder half way through the book. We eventually discover (sort of) who did it, but it was a political murder and the solution was dismissed in a couple of lines.
The book began in a monastery for scientists/philosophers and wandered off to outer space, and I wandered with it. Only a fanatic would read the parts that wandered off on philosophical tangents. I did not understand said parts, but I must be a Stephenson fan(atic) because I read them.
I think in a parallel world I really liked the story. In another parallel world I really didn't like the story. In this world I mostly liked it.
If it had been a mystery, there would be more to this review. But now I must turn out the light on a book that has been a part of my life -- part of my family, even, for it sat at my breakfast and dinner tables -- for many weeks now. Somnus in pacis.