Richard Preston's recent best-seller, The Hot Zone, told the story of the new plagues that threaten humankind. But his skill as an expert storyteller who makes documentary as gripping as a good novel was already known to astronomers, thanks to First Light. Never published in Britain before, and long out of print even in the US, it has been an underground classic among astronomers for 10 years, with dog-eared copies passed from hand to hand like some samizdat pamphlet in the old Soviet Union. Now, First Light is available in paperback for everyone to enjoy.

Apart from the fact that he is a superb writer, the secret of Preston's success is that he lives with his subjects (in this case,astronomers) for so long that he blends into the background. He can make notes like an anthropologist in the forests of Africa. The astronomers were a group at Mount Palomar, California, in the Eighties. They were using the 200- inch-diameter Hale telescope to probe quasars at the edge of the visible universe.

The result is not the best book ever written about astronomy - the science is now slightly out of date, and some of the facts are slightly wrong. But it is undoubtedly the best book ever written about astronomers, and one of the best ever about how scientists work. Anyone who knows the characters here knows how accurate Preston's portrayal is, and there is no better depiction of the obsession that drives people to do this kind of work.

The central character, though, is the telescope itself, a monument to the driving ambition of Edwin Hubble, built largely during the great depression of the Thirties. In a sense, this was the last great achievement of 19th- century technology: a giant telescope a generation ahead of its time, which modern instruments are only now beginning to surpass. With its builders now dead, there is nobody alive who understands quite how it works. It is kept running by "gadgeteers" from Caltech who beg surplus parts from richer institutions, literally rummage in refuse bins, and apply liberal quantities of a sticky tape known as "Palomar glue" to hold things together.

The book, though vastly entertaining, is not without its chilling moments - especially when Preston describes a breakneck ride across the Arizona desert, driven by Gene Shoemaker with his foot to the floor in an overloaded Plymouth Fury.

A few months ago, Shoemaker, by then famous as co-discoverer of the comet that smashed into Jupiter in 1994, was killed in a car crash while hunting meteor craters in Australia. In a way, this fits the theme of the book, which wistfully contrasts the brevity of a human life span with the immense ages of the objects astronomers study.

First Light is the best book about science you are likely to find for a very long time. And the best time to read it is now, in the depth of winter, when you can put it down, go outside, look at the night sky and imagine what the view must be like from Mount Palomar.