At its best, Mr. Friedman’s This Dog Will Change Your Life is an exploration of how human dogs really are ... One of Mr. Friedman’s most striking chapters, on adoption and dog shelters, deals with the elements that make a shelter dog more likely to stand out ... It’s a pity, therefore, that much of Mr. Friedman’s book meanders away from this central and provocative throughline ... Often feels like an unnecessary gloss upon the author’s otherwise engaging photographic work ... Distracting, too, is Mr. Friedman’s too-cute insistence on avoiding academic research or jargon ... This lack of focus makes it impossible to tell what kind of book This Dog Will Change Your Life is supposed to be—beyond, one supposes, a requisite extension of an established brand ... Mr. Friedman does, it seems, have a book’s worth of worthwhile things to say. When he gives himself the freedom to write with greater detail and precision about his own artistic process—the act of photographing dogs and how it differs from photographing human subjects—we get a glimpse of the book that might have been ... All too often, alas, the unfocused nature of This Dog Will Change Your Lifemakes the book feel like a requisite gift for self-identified dog-lovers, or The Dogist fans, rather than a book intended to be read.