Axiomatic is a collection of eighteen short stories by Greg Egan, the Australian author of Quarantine and Permutation City. Egan's ideas stretch your head the way the better cyberpunk does, without cyberpunk's self-indulgent grime and alienation.

Most of the stories center on questions about the nature of consciousness and the definition of self. Egan has an improbable knack for making this sort of solipsistic navel-gazing interesting. "The Safe-Deposit Box" is about a man who wakes up in a different body every day, and dreams of having an identity of his own. In "Learning To Be Me", durable artificial devices implanted in everyone's brains learn to precisely simulate their consciousness. A person's organic brain is disposed of once it starts to degrade, but has the original person died or merely "switched?" In "The Infinite Assassin", parallel realities are fractured and swirled together, and an agent must work with all his parallel selves to stop it.

"Unstable Orbits in the Space of Lies" describes a future in which ideologies function like gravity: Anyone within a certain radius of a sufficient number of True Believers becomes an adherent of that system of belief. "Into Darkness" is a rescue story set inside a malfunctioning time tunnel that wipes out whole neighborhoods unpredictably. In "The Hundred Light-Year Diary", scientists have learned to send information into the past, so the events of both public history and private lives are known before they happen.

The better stories -- most of them -- explore the effects of various flavors of superscience on ordinary people. The weaker stories suffer from Egan's tendency to describe the core idea in pedantic narration or dialogue. Even the stories that fall flat are thought-provoking, however, and several are genuinely disturbing. Fans of hard SF and cyberpunk should enjoy Axiomatic.