The ROI on this book is incredible. To be fair, it's easy to get ROI on a $10 book, but I ended up with an extra $40k-ish on a salary negotiations over the years because of some of the details in there. You just need one or two to hit. The hyper specific number idea surprisingly worked for being a pretty goofy concept to me at first.
Not only did these techniques save me money, but they also saved me a considerable amount of time. I've employed these same strategies at work and private to navigate away from requests and projects in which I have no interest.
It's a good book, but I've read it a few years ago and already forgot most of it. I gather you need to refresh this knowledge just before you negotiate.
Clear actionable direction on how to negotiate.