I'd seen interviews with Jason Fung and heard about the benefits of fasting and wanted more info before trying it. I've found this book to be a helpful guide. it covers various types of duration for fasts, goes over the health bits and also addresses questions and some of the mental stuff and how I think about food which I found relevant. I got it in kindle format so maybe not as great to navigate/view charts as hardcopy would be. I'm happy with the book, doing 24 hr fasts a couple of days a week and building up to 5 day.