R. C. Jennison New York: Philosophical Library Inc. 1967 Pp. viii + 160. Price $4.75. In the last twenty years radio astronomy has developed into one of the most fascinating areas and growing points of modern scientific research. There have already appeared several popular books on the subject, also one or two text books of an advanced nature, but Professor Jennison in his most readable little book has tried to provide something in between these two approaches.