This book began as a kind of primer for mature students, but grew into something with wider appeal. For most people, radioactivity is a vaguely understood phenomenon. Books that explain it are usually written by specialists; technical jargon is abundant and the lay reader often struggles to sort information. This does not happen in "What Is Radioactivity? The Basics." Material is presented in manageable blocks so that unfamiliar concepts, such as ionization and artificial radioactivity, are easily grasped. The book not only explains radioactivity, but also offers a brief history of its discovery. The great names in atomic and nuclear science are discussed, going all the way back to Democritus. Curie, Fermi, Bohr--and others--are introduced. The context of atomic bomb development and the accompanying moral dilemma are addressed. "What Is Radioactivity? The Basics" achieves its goal partly through liberal use of photos, including one of the first x-ray ever taken. This book would surely be frustrating reading for a scientist. The rest of us, however, likely will finish reading it with what had been promised, a basic understanding of radioactivity and the very consequential issues attached to it.