A. C. Grayling is a "professional philosopher," and those of us that enjoy all that professional philosophy bring us are easily happy with this and his other books.
BUT, this book, like a series of publications storming the citadel, are not of the "professional" arcane nuanced kind. These short essays go directly to most of our practical concerns, without the arcane language of epistemology, axiology, praexeology, ontology, and more sophisticated subjects.
BUT don't think this material "light weight." It's merely accessible, in ways that professionals get tongue-tied using the Greek fundamentals. Following the success of Robert Solomon's corpus, Grayling is more succinct, just as valuable, and even more accessible.
Maybe, now, we can engage metaphysics of psychology, religion, superstition, voodoo, and chiropractic -- with the hard facts, the known classical values, and even upend the "traditional biblical moral values" and all the hypocrisy with humanistic values. If any two philosophers can, Solomon and Grayling are it.
So, are the other (supra.) reviewers out of it, or simply opposed to humanistic values of knowledge. Read Grayling and discover the answer for yourselves.