Hispania, the official journal of the American Association of Teachers of Spanish and Portuguese, has published a review of ¿Por qué? in their June (2018) edition. It is a most complimentary review, with adjectives including “delightful,” “engrossing,” “meticulously researched,” “a joy to read,” “concise,” “brisk,” and “accessible though erudite.” The only thing that would have made me happier is if it had included the magical phrase “Every Spanish teacher should buy this book.” But you can’t have everything!
You can download a copy of the review here. It starts on the second page of the PDF.