To Explain the World, about a subject that has fascinated him for a long time: the discovery of science. First, the book takes us to the old Greeks. The civilization in Ancient Greece is generally divided into three era's: the Archaic era (roughly from 800 to 480 BC) with Athene as its center and great thinkers like Thales, Heraclitus, and Democritus, The Classical era (roughly from 500 to 323 BC) with Athens as its center and Socrates, Plato, and Artistotle as its main philosophers, and the Hellenistic era (from 334 tot 30 BC) with Alexandria as its center and Euclid, Ptolemy, and Archimedes as its greatest thinkers.
Weinberg shows how thinkers in each of these era's have made unique contributions to the emergence of science. To try to summarize those contributions briefly: Archaic: asking questions about nature and formulating hypotheses; Classical: asking critical questions about the validity of ideas, emergence of many disciplines, development and refinement of taxonomies, and methodologies among which logic; Hellenistic: strong development of math and physics and many technological applications.
The book continues with some contributions from other periods (such as the Middle Ages) and areas (such as the Arabic world), after which it proceeds to antecedents of the scientific revolution, like Copernicus and Kepler, and to the start of the scientific revolution itself with Galileo Galileï whom Weinberg considers to be the first real full blown scientist in the modern sense of the word. In his first book, this Italian proved Copernicus' heliocentric model to be right and this brought him into conflict with the church after which he was commuted to house arrest. After his second book was smuggled to the liberal Holland it was published there. Only in 1992 the church admitted its errors and expressed its regrets. What were great breakthroughs during the scientific revolution was that experiments started to play a much more important role in the development of knowledge and that published results were offered as evidence of ideas. The path was now clear for geniuses like Newton, Darwin, and Einstein.
Weinberg has not only received admiration but also some criticism for the book. This criticism focused among other things on the fact that he looks with modern eyes at earlier thinkers and criticizes them based on what we now know. I don't agree with this. I think Weinberg's approach is actually justified and interesting. A second criticism, one which I do share, is that the author pays very little attention to China's and India's contributions to the development of science. A third criticism, which also share to some extent, is that he emphasizes physics at lost at the expense of other sciences such as biology. Although I do think this is justified criticism I must also admit that physics does deserve a special place in the history of science and came to maturation a bit sooner than other areas of science.
Conclusion: if you find history and science interesting you will probably like this book a lot.