Book excerpt: What is income inequality? How is it measured? Is the middle class really declining? How does it relate to poverty? How long has inequality been rising in the US? Have there been other periods in history when income differences were as large as they are today? What are the causes of growing income and wage inequality? The author addresses these and other conceptual issues in eight carefully reasoned and clearly presented chapters. Concluding with an analysis and comparison of trends in wage inequality in other developed countries, he asks the final speculative question: How much more growth in inequality can our society withstand?