This is an extraordinary book.
It's difficult to imagine a more flagrant breach of xkcd's fiction rule of thumb, especially since one of the made-up words is actually "fraas".
And for this reason, the first few chapters of this massive book are heavy going.
But there's just enough of interest to start to draw you in, despite the seemingly needless difficulties caused by repeatedly making new words for both familiar and unfamiliar things.
You rapidly get comfortable with the strangeness of Fraa Erasmas' world, and are slowly drawn into the detective story which is one of the main themes.
Soon there are terrible injustices and secret conspiracies that are crying out to be explored and rectified. Small strangenesses start to pull apart the fabric of the world and its history.
Like all really classic fiction, the novel manages to evoke a world of vast age and wonder, without ever really going into details about it. As well as the actual story, there is a huge hinterland to be imagined, and you start to really care about the exploits of ancient philosophers and long dead saints who aren't mentioned more than in passing in the text. There are hints of ancient technologies, now lost, and hints of conspiracies, and hints of technologies so far advanced that they are indistinguishable from magic. Echos of ancient horrors, and hidden reasons, and secret cabals.
The book launches ambitiously into maths and logic and physics and their philosophy. Geometry, Dynamics, Platonism, Sophism, Formalism and consciousness itself are discussed by the characters as they grope towards quantum mechanical formulations. The influence of Penrose and Deutsch become obvious as the Hylean Theoric World of the ancients becomes a flow in a vast phase space.
The book becomes simultaneously a book about ancient magicians and alien invasion.
The triumph is that all of this works. The philosophy seems vital and important. It's not side material. It's the plot. There's no contradiction between the wizards and the scientists. There are genuine mysteries and moments of heartache.
If Cryptonomicon was nine-tenths of a barnstorming novel followed by a surprisingly weak ending, Anathem is a true masterwork with a slow start and a climactic ending which is damned near incomprehensible.
It took me four days to read this book. I am going to give myself a couple of days before I read it again. There is no way that I am not going to read it again. I feel utterly compelled to try to work out what the hell was going on.
Ever since I finished reading it there have been bombs going off in my brain.
I can't think of a higher compliment to pay to the author.
I can imagine, as with "The Mote in God's Eye", that some people might not like the setting and style. I cannot imagine that anyone with an interest in intelligent science fiction would not be pleased to have read this book.