First, what this book is not: a book about ending aging. For that, you would want to check out “Ending Aging”, by Dr. Aubrey de Grey.
What this book actually is: a book about the purpose of aging. As in: “aging: to what end?”, and then the book answers that question.
Rather than viewing aging as solely a source of decline, this book (while not shying away from that) resolutely examines the benefits of old age—from clinically defining wisdom, to exploring the many neurological trade-offs (e.g., “we lose this thing but we get this other thing in the process”), and the assorted ways in which changes in our brain change our role in society, without relegating us to uselessness—far from it!
The style of the book is deep and meaningful prose throughout. Notwithstanding the author’s academic credentials and professional background in geriatric psychiatry, there’s no hard science here, just comprehensible explanations of psychiatry built into discussions that are often quite philosophical in nature (indeed, the author additionally has a degree in psychology and philosophy, and it shows).
Bottom line: if you’d like your own aging to be something you understand better and can actively work with rather than just having it happen to you, then this is an excellent book for you.