Brittany Kaiser, Harper, 400 pages, $28.99. What do you do if you want to sell Coke in a movie theater? For decades advertisers thought they had it figured — ads throughout the movie theater and on the screen before the movie. But what if instead you asked under what circumstances would they drink more Coke? You would find it was when they were thirsty. So you turn up the temperature in the auditorium. The solution isn’t in the ad but the audience. Thus does Alexander Nix, CEO of political consulting firm Cambridge Analytica, outline the fundamentals of persuasion in the digital age to Brittany Kaiser. Kaiser, his head of business development, would subsequently turn whistleblower and is now the author of “Targeted: The Cambridge Analytica Whistleblower’s Inside Story of How Big Data, Trump and Facebook Broke Democracy and How It Can Happen Again.” The book is a rarity, both important and gripping. It is Kaiser’s account of her time working for SCL Group and its spinoff company Cambridge Analytica. And it is a vital story to tell. CA, as it is known, is widely believed to have aided Donald Trump’s election in 2016 by illicitly harvesting the personal data of millions of Facebook users to better target them with political advertising. Election chicanery and online malfeasance: “Targeted” could not be more contemporary. But what makes Kaiser’s book so vital is that it covers far more than just this. Beyond the story of the rise and fall of Cambridge Analytica, it is about the experience that awaits all of us in a society that has reconfigured itself around a new and overarching source of power: data.