The Day the World Discovered the Sun covers the historical adventures involved in, and the build-up surrounding, the 1761 and 1769 transits of Venus.
It was posited by Edmund Halley that by using these transits it would be possible to calculate the distance between the Earth and Sun to a 98% certainty and so it proved, unfortunately Halley died before the transit occured.
The book details, in addition to the myriad far-flung voyages to record the transits (Vienna, St. Petersburg, Mexico, Baja California, Siberia, Paris, arctic-circle Norway, South Pacific islands, Barbados, Cape Town, Tierra del Fuego, Copenhagen, Jakarta, Cadiz, Rio de Janeiro) the critical leaps in progress made in oceanic navigation, and in astronomical calculations such as the precise distance from the earth to the sun, during this fruitful period.
As well as about the transits its the people involved and the sheer obsession to record the transits.
i didnt feel it was the most gripping of books, whilst interesting it didn't fully engage me.