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Great Comets sounds like a remark startled from Superman. In fact it’s a fine book on these celestial wanderers, in which Robert Burnham describes what they are and how their mysteries have been unravelled in recent times. Plans to intercept them and land probes on them get an airing-and he doesn’t forget the occult significance of comets in history. Published by Cambridge University Press, £12.95, ISBN 0521646006.