The purpose of this book is to define the concept of relativity in terms that the intelligent layman can understand.  

The book is written in nontechnical language.  The reader need not have had more than a little high school geometry to understand what is being discussed.The book is planned so that the text and illustrations face each other on a two-page spread, making it easy for the reader to refer from text to illustrations.

The author begins by asking two questions: What is Time? and What is Space? Time: At first we think we know, because we feel time is that which passes and whose passage separates the earlier from the late.  Our first notion of time is merely qualitative; days may seem short or long, an hour may be endless or may vanish in an instant.  We develop quantitative notions of time in terms of physical events; however, this notion of quantitative time is derived from physical experience and can be changed when experience seems to warrant change.  Space: We have direct quantitative experience of space also; the distance from object to object and place to place is called near or far, depending on what our experience has taught us to call near or far.  Quantitative notions of space are arrived at through experience and measurement of space.  These notions may also be changed when the details of experience warrant it.

The author then proceeds to discuss the law of uniform motion and the way in which quantitative notions of space and time of one uniformly moving observer are related to those of another uniformly moving observer.

taking Mr. A. and Mr. B. as his moving observers, the author shows how the notions of time and space of Mr. A differ from those of Mr. B.  In the author's own words we find that "the laws of physics are such that a moving observer does not agree with a fixed observer as to which sets of events occur at the same time but has different notions of time and space...hence quantitative time is not an absolute property of the universe.

As it is evident form this brief summary, the reader who follows the carefully constructed exposition will end up understanding the basic parts of relativity.  

The intelligent adult, the scientist who may not have studied the subject and wants a quick account, and students from high school through the first year of graduate school will find this book engrossing and challenging.  Its clear, well balanced exposition of the theory of relativity will be read with interest and profit.  Here is an excellent introduction to one of the most important physical theories of the twentieth century.

From the dust jacket