This unusual title combines X-ray photographs of once-living animals with a chatty, relatively lengthy accompanying narrative about the subject and what can be seen. These images are the attraction. Photographer van ’t Riet, a former medical physicist, has posed his subjects carefully, often among leaves and flowers that have touches of color. In traditional X-rays, solid parts show up white; here, most images have been reversed so that the animal and its innards appear in grayscale on a white page. The occasional use of original images on black backgrounds provides variety. Introductory sections describe how the images were made and what an X-ray photograph actually is. Since it’s not easy to obtain dead animals for this purpose, what’s presented clearly reflects availability, but the emphasis is not on learning about these creatures but on marveling at the intricacies of their insides—how similar they are and how different. There are six sections: arthropods and mollusks, fish, amphibians, reptiles, birds, and mammals. In general, each of the 50 animals gets a spread. A conclusion describes the discovery of X-rays. Originally published in the Netherlands in 2017, the text has been ably translated from the original Dutch by Watkinson, and there is an unusually detailed index that includes the questions that have been answered for each animal.