Arsibalt: A fraa from Math of Saunt Edhar, and one of Erasmas' friends.
Jesry: A fraa from the Math of Saunt Edhar, and one of Erasmas' friends. Unlike Erasmas, Jesry is from a burger family, and is bored with the routine Mathic life leading up to his evokation. He becomes famous for going into space with the Warden of Heaven to investigate the Geometers' ship.
Lio: A fraa from the Math of Saunt Edhar, and one of Erasmas' friends. He shows great interest in vlor (vale lore) and all forms of weaponry and warfare.
Ala: A suur from Math of Saunt Edhar, and later a major organizer of the Convox. Though they do not like each other initially, she and Erasmus develop a relationship throughout the book.
Jad: A millenarian from the Math of Saunt Edhar. Jad is evoked in the same aut as Erasmas, and accompanies him to Bly's Butte in search of Orolo. Later reappears at the Convox.
Orolo: Erasmas's main teacher and influence at Saunt Edhar. He recruits Erasmas into the Edharian Order, but is later Thrown Back for attempting to observe the Geometers long before their existence was confirmed. He dies at Ecba while saving the corpse of a Geometer.
Sammann: An Ita of Saunt Edhar, who accompanies Erasmas to Ecba after his evocation.
Cord: Erasmas' sister, who lives in the saecular world outside of Saunt Edhar. She accompanies Erasmas to Ecba after his evokation.
To create the world of Arbre, Stephenson created an entirely new vocabulary. In order to familiarize the reader with the new words, many of which are analogous to English words and ideas, he put a glossary at the end of the book. Each chapter begins with a definition of one of these words, which usually relates to the chapter in some way. The title of the book takes its name from anathem, a mathic ritual by which one is expelled from the mathic world. The word is a dual derivation of "anthem" and "anathema."
Michael Dirda of the Washington Post disagreed, remarking that "Anathem will certainly be admired for its intelligence, ambition, control and ingenuity", but describing it as "fundamentally unoriginal", "grandiose, overwrought and pretty damn dull.
The novel entered the The New York Times Best Seller list for Hardcover Fiction at number one.