What is the author's tone in A Brief History of Time by Stephen Hawking?

Hawking's editor warns him not to use very many mathematical equations in his work, as each equation presented cuts readership in half. The author accommodates this request and only gives one equation, Einstein's energy equals mass times the speed of light squared. The author's use of prose, to describe how theories work and what they mean regarding the nature of the universe, generates a conversational style sprinkled with humor and analogy. He occasionally takes side trips from the main idea, which he usually builds to and brings home toward the end of each chapter. The chapters flow from one to another, completing a very large scope within a relatively short book, as a brief history should be.