This is a series of podcasts put out as an audiobook. I highly recommend it, but if you're looking for an answer to the title question (Who killed truth?), you're not going to find it. What you're going to find are a series of fascinating historical vignettes. I was familiar with several of them but still learned new details about them. The subtitle (A History of Evidence) is a more accurate description of the book, but even that oversells it, in my opinion.
My two main criticisms of the book were that the audio files used to illustrate points were sometimes too hard to understand (and there wasn't a synopsis of what was said, which would have cleared up the confusion), and I could have done without the last section of the book, in which the author goes to two New England high schools to determine if high schoolers should be the arbiters of what political ads get posted on social media. It showed that many New England high schoolers are bright and engaged, but I laughed when she said that she was choosing high schools that were on different ends of the spectrum--one in New Hampshire and one in Vermont. If she really wanted diverse high schools to prove her point, she should have taken two that were more diverse, such as a New England high school and a Compton, California, or rural Iowa high school, for example. (I realize that would have posed more difficult production problems, but it would have made the "study" more valid, in my opinion.)