Jared Diamond's Guns, Germs, and Steel: The Fates of Human Societies was originally published in 1997, so if you're at all interested in anthropology and haven't read it by now, you should really pick up a copy.

In this book, Diamond examines the technological and economic inequality between civilizations around the world throughout history, and how these gaps in power came to be. The answer doesn't lie in any sort of natural/genetic superiority of any given civilization over others, but rather in environmental differences such as geography and ecology.

The book's Wikipedia page actually sums up Diamond's thesis well:

The first step towards civilization is the move from nomadic hunter-gatherer to rooted agrarian society. Several conditions are necessary for this transition to occur: access to high-carbohydrate vegetation that endures storage; a climate dry enough to allow storage; and access to animals docile enough for domestication and versatile enough to survive captivity. Control of crops and livestock leads to food surpluses. Surpluses free people to specialize in activities other than sustenance and support population growth. The combination of specialization and population growth leads to the accumulation of social and technologic innovations which build on each other. Large societies develop ruling classes and supporting bureaucracies, which in turn lead to the organization of nation-states and empires.

Reading that page doesn't quite offer the same breadth of insight found in the book itself, so I still recommend getting a copy to read for yourself. You can find it in these formats:

• Kindle ($10)
• iBooks ($10)
• Hardcover ($18)
• Paperback ($11)
• Audible audiobook ($27)
• Audiobook (CD) ($19)

The 2005 documentary based on the book is also worth a watch.