A cavalcade of clocks. Rooney, the former curator of timekeeping at the Royal Observatory, Greenwich, takes readers on a dramatic historical tour of horology to show what clocks mean; how, over thousands of years, they became more precise; and how time itself “has been harnessed, politicized and weaponized.” The author delivers a lovely, personal, idiosyncratic “story centered on power, control, money, morality and belief.” Rooney traces the development in timekeeping instruments, from the earliest sundials to an acoustic water clock that may have existed in the city of Verona in the early 500s to a plutonium time-capsule clock buried in Osaka in 1970. Automaton water clocks spread across the medieval Islamic world to remind its citizens of who was in power, and the first mechanical and astronomical clocks flourished throughout Europe after the 13th century. Gradually, Rooney notes, a new idea was born: “that time could be wasted.” The author chronicles his visit to Siena to observe a painting from 1338 that prominently features the “oldest known depiction of an hourglass.” This timepiece, he writes, represented “the cutting edge of horological technology” that would impact the way Western civilization thought about right and wrong, life and death. In the 1610s, Amsterdam’s groundbreaking stock exchange erected “one of the most significant clocks ever made…sounding the birth of modern capitalism.” In 1732, the Indian city of Jaipur constructed the largest sundial ever. The rise of coastal time signals—balls, discs, guns, or flags—“spoke volumes about the shifting sands of global geopolitics.” Rooney also insightfully explores the ramifications of electricity and the creation of standardized time, which had a controversial, even violent, cultural impact: “we have poured our very identities into clocks.” Somberly, the author writes about the “The Clock of Doom,” designed in 1947, which reminds “us what happens when time runs out.” Throughout, Rooney entertains with witty clock trivia and anecdotes alongside illuminating sketches of famous horologists. Go slowly when devouring this charming, intelligent, highly informative history.