This book brings together a selection of questions submitted by readers of Science Digest, which Asimov answered over the years in a section titled Please Explain. The answers are written in an accessible language, with the clear and engaging style that characterizes the author, and cover topics such as the scientific method, relativity, black holes, evolution, the structure of the universe, imaginary numbers, among others.

It is not a technical treatise, but a guide to spark scientific curiosity and foster rational thinking. Asimov avoids dogmatism and focuses on explaining complex concepts in a way that is understandable for the general reader.

Some scientific explanations may contrast with religious interpretations, but there is no polemical intent.