Within philosophy of science, debates about realism often turn on whether posited entities exist or whether scientific claims are true. Natural kinds tend to be investigated by philosophers of language or metaphysicians, for whom semantic or ontological considerations can overshadow scientific ones. Since science crucially involves dividing the world up into categories of things, however, issues concerning classification ought to be central for philosophy of science. Muhammad Ali Khalidi's book fills that gap, and I commend it to readers with an interest in scientific taxonomy and natural kinds. He works through general issues to craft a useful philosophical conception and uses the account to think through a wide range of specific examples. Although there are differences in the details, that one-sentence summary of Khalidi's book could just as well describe my own recent monograph on natural kinds.
Magnus, P.D., "Epistemic categories and causal kinds" (2014). Philosophy Faculty Scholarship. 22.