This is the best book I've read on the topic of fasting. Good writing style, information seems reasonably accurate using "common sense method" of evaluating. Still only limited scientific studies on fasting (at least in humans) and time restricted feeding but the practice has been around since the beginning of time (at least until rather recently in human history) so I would think using common sense when deciding if a concept/principle sounds reasonable (in theory) would be of some value. His description of physiological processes such as insulin and fat storage or the body's ability to mobilize fat (or not) under certain conditions is accurate.
Overall, the concepts he presents are reasonable and his case study examples are believable. Easy to read, good writing, informational. Definitely worth the read!