It's a catchy title, and I suspect that's why it became a bestseller. Although categorised as "popular economics" on the back cover, this is in fact a quasi-academic treatise, full of data compiled by the authors and others. In fact there's not much material going back eight centuries; most countries don't even have data going back as far as 1800. But nevertheless, it's a valid point.
The authors have three main strands of analysis: external sovereign debt, domestic sovereign debt, and banking crises. Each of these is chewed over in turn to determine patterns and lessons. The good news is that some countries have no recent history of external sovereign debt (that is, debt owed by a state to entities outside its borders, denominated in external currencies), although almost all countries have a history of serial default if you go back far enough.
On domestic sovereign debt (debt owed by a state denominated in its own currency and generally owed to entities within that state), the picture is less clear. There's a sliding scale between inflating away debt to outright default, and governments generally massage figures.
On banking crises, the picture is possibly worse, as the authors argue these are generally frequent and of similar character in both developed and emerging economies, typically provoked by asset bubbles and unsustainable capital movements.
Finally, the authors turn to the recent global crisis, arguing that whilst it is severe, it nevertheless follows many of the characteristics outlined and therefore shouldn't have come as much of a surprise to anyone. They have a handful of measurements they recommend to policy makers, but no easy solutions.