More specifically, Bhalla makes the following points: (1) Income inequality is declining across nations (in large part because of rapid income growth in poor populous nations such as China and India in East and South Asia). (2) Income inequality is rising in many nations. (3) Because inequality across nations is the larger component of total world income inequality, total inequality is declining despite the rise in inequality in the average nation.
Unless you have time to spare, however, I recommend you read The New Geography of Global Income Inequality instead of this book. It's more expensive than the Bhalla book, but it's also a much better book - more focused, better organized, more convincing, and more theoretically informed. In fact, if not for the price of The New Geography, I would recommend it for college courses in globalization and economic development. I would not recommend Bhalla's book for undergraduates. In addition to The New Geography, I also recommend the September 2002 article in the American Economic Review by Bourguignon and Morrisson, "Inequality among world citizens, 1820-1992."