I remember this being such a massive bestseller when I was a bookseller, and it inspired lots of scholarly but little books popluarising odd scientific and historic stories that was rather wonderful to behold. Longitude itself is a wonderfully succinct, heartfelt account of the problem of longitude, that is, the problem of discovering which longitude you were at while at sea, a life-or death matter. Ultimately solved by the craftsman-genius John Harrison and his clocks as he more-or-less singlehandedly dealt with a number of seeming implacable mechanical problems associated with ocean-going time-pieces. His trials and travails in claiming his reward are somewhat heartbreaking, but ultimately this is a moving account of how one man's invention made one of those profound changes that has become part of everyday life and utterly taken for granted nowadays.

At one point, though, she remarks that Harrison's invention enabled the spread and dominance of the British Empire, which, even if an exaggeration, puts a different spin on it, and one which Sobel shys away from instantly. The uses of navigational tools for the purposes of global subjugation and domination would presumably be a different sort of story to the charming little biography that went on to become so massively poplar.