This is a concise, expert summary of Theravada Buddhism covering Buddhism as an "attitude of mind" (Chapter 1), the Four Noble Truths (Chapters 2-5), doctrine and practice (Chapters 6 & 7), and its continued relevance in the modern world (Chapter 8). The book concludes with selected classic texts from the Pali canon. The author, Venerable Dr. Walpola Sri Rahula, was a monk and Buddhist scholar. His doctoral thesis was on the history of Buddhism in Ceylon.
I had explored Buddhism occasionally, on and off for nearly 40 years before I found this book. This was the clearest overall exposition I had read--or have since--of Buddhism overall, and after reading it completed my explorations: I became a Buddhist. There are, to be sure, far better books on practice, but reading this first gives a very solid foundation for the practice.