One book that comes to mind is The Rise and Fall of the Great Powers (1987) by Paul Kennedy. This hefty book examines the political, military, and economic foundations of empires since roughly 1500 and the reasons why all these nations eventually enter a period of decline.

The "imperial overstretch" theory that Kennedy proposes with this book states that all empires will reach some sort of critical mass at which the empire can no longer support the military and economic costs of its vast holdings. The book analyzes the economics of empire from the Ming Dynasty, to the modern United States, and everything in between. Definitely worth a read; my political science professors still discuss Kennedy's theories RE: the inevitability of American decline.