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Sleep is an ancient, universal experience. But it is only in the past half century or so that it has attracted the attention of dedicated researchers. A new book from Kenneth Miller sets out to record the field’s short but fascinating history.

The early pages of the book, before there is much in the way of established science to describe, are the weakest. A good deal of time is spent on biographical details and portraits of the world through which Nathaniel Kleitman, an influential scientist working on sleep, moved. But the story soon picks up. It roams (漫步) from the discovery of rapid-eye-movement (REM) sleep to the effects of sleep shortage.

One section even describes a modern quantitative research of circadian-rhythm — the biological clocks that govern human’s days — that took place in a purpose — built facility in a Bavarian village. The lab sported two apartments, with no window or clocks to clue their subjects into what was happening outside. Test subjects lived there for weeks, free to wake and sleep whenever they liked — but never free from the thermometers (体温计) that were attached to the wall by long electric lines.

There is a serious side, too. Shift work interferes with the body’s internal clocks and raises the risk of illness. Mr. Miller also explains the slow recognition of sleep apnoea, a common sleep disorder, and the damage it can cause.

Discoveries often lead to new questions in turn. That is why neat, tidy endings are hard to achieve in science books. Despite all the progress of the past 50 years, scientists are still unsure what sleep is for. The fact that it is so widespread suggests it is vital. But why evolution would see it fit to produce animals that must spend large amounts of their time unable to respond to threats is still a mystery researchers are trying to solve. For anyone curious about asking the right questions, however, Mr. Miller’s book is a good place to start.