This is a not unpleasant little pamphlet Asimov prepared for the Atomic Energy Commission with geneticist Theodosius Dobzhansky listed a “collaborator” on the title page. Asimov had a number of collaborators officially listed on the title pages of a number of the early books which he himself actually wrote. In this case, the AEC had originally contacted Theodosius Dobzhansky, but Dobzhansky felt unqualified to do such writing and suggested Asimov. Asimov felt unqualified to cover the material, however, so the AEC arranged for Dobzhansky to backstop him in terms of content, which turned out to be a workable solution.
(An aside: I find it rather ironic that Asimov in the earlier stages of his career was occasionally saddled with listing a “collaborator” as a co-author for a book—e.g., Races and People, Planets For Man—when the collaborator had little actual involvement in the writing of the book, when at the end of his career the tables were turned and Asimov’s name was often slapped onto a book as a “collaborator”— Robots: Machines In Man’s Image springs to mind—when he actually had little to do with the book.)
Asimov here covers much of the same information about radioactivity and its effect on human tissue rather to the same extent he did in Understanding Physics, volume three. The actual contents of the book are therefore a more focused rehash of the earlier material (with more pictures). This means that there’s nothing actually wrong with it, but neither is there really any point to get a copy—as if that were possible—when one can far more easily get Understanding Physics.