A lot of fun to read and quite informative for newbies like me. It goes over the most common vulnerabilities, explains their concepts in a basic manner, and details examples of bug reports that were posted on HackerOne, and whether they got paid for it or not. The last chapter also includes useful guidelines for getting started.
Beware that you might need to be familiar with web concepts before attempting to read this book. Although it tries its best to explain everything, it's often attempted in one or two lines and that's not enough unless you have first-hand experience with the technologies mentioned. Knowing HTTP, HTML, and basic JavaScript would be the minimum requirement for getting anything out of this book, I'd say.