The Eternal Flame: Orthogonal, Vol. 2

Readers unfamiliar with 2011’s The Clockwork Rocket, vector mathematics, and the physics of light are likely to stumble through this dense sequel, which puts the “hard” in hard SF. The series’ intriguing underlying premise is apparently that light in the “Orthogonal universe” can travel at different speeds even in a vacuum, but this is never spelled out in the text. The natural laws governing this universe are detailed only in an afterword (which itself follows three appendices) that’s laden with sentences like “Because there is an upper limit on the frequency of light there is no ultraviolet catastrophe, and the spectrum predicted by classical physics is only slightly different from the true, quantum-mechanical version.” Pages of clunky scientific discussion within the book proper also stifle the plot about an alien race’s struggle to avoid the threat of meteorlike objects. Egan’s tendency to bludgeon readers with esoteric detail will be a turnoff even for those who like fiction that assigns homework. (Sept.)