Light marks that fine writer M John Harrison's first return to the heartland of SF--including spaceships and hair-raising interstellar chases--since his apocalyptic anti-space opera The Centauri Device (1975). The heavy SF action begins in 2400. Space-going humanity is the latest of many civilizations to be baffled by the impenetrable Kefahuchi Tract; that vast stellar region where an unshielded singularity makes physics itself unreliable. Along its accessible fringe, the "Beach", solar systems are littered with crazy, abandoned devices used to probe the Tract since before life began on Earth. A whole dead-end culture is based on beachcombing this rubble of industrial archaeology... 25th-century characters include a woman who's sacrificed almost everything to merge with the AI "mathematics" of a crack military spacecraft; a former daredevil who once surfed black holes but has retreated into a virtual reality tank; the lady proprietor of the Circus of Pathet Lao, with an alien freakshow and a hidden agenda; and a variety of raunchy, smelly, gene-sculpted lowlife, some comic, some menacing. Many are not what they seem. Meanwhile in 1999 London, physicists Kearney and Tate--remembered in 2400 as the fathers of interstellar flight--are getting nowhere. Kearney's personal problems occupy familiar Harrison territory: urban paranoia, a seedily unreliable guru, bad sex, guilty rituals to propitiate a metaphysical-seeming threat called the Shrander--a pursuing image out of nightmare. In the lab, both Kearney and Tate fear the increasing quantum strangeness of their results. The cosmological wonders and hazards of the Beach form a backdrop to space pursuits and violent skirmishes whose duration is measured in nanoseconds, reported in tensely lyrical prose. Eventually everything comes together as it should--even that oppressive 1999 story strand--with revelations, transformation, transcendence, and ultimate hope. Harrison demands your full attention and rewards it richly. -- David Langford