Rounding this up from a 3.5; I liked it, it was very readable (and I feel like I can explain the basics of relativity now), but it's astounding to me that someone would write an ideas-focused overview of the twentieth century in the West without covering racism and the civil rights movement. (Especially given that this book covers rock'n'roll but explicitly describes it as "music aimed directly at white teenagers" despite naming that particular chapter after the first line in "Tutti Frutti".)