James Chambers:

"The Devil's Horsemen - The Mongol Invasion of Europe" (1979)

(Copyright © 2006 Piero Scaruffi | Legal restrictions - Termini d'uso )
It only deals with the "western" part of Mongol history, but the book sheds a lot of light on the workings and innovations of the Mongol empire as a whole. The Mongols were vastly more "civilized" than they are usually depicted by the historians of the countries that were conquered. Their military strategy was unsurpassed. Their communication system was as sophisticated as it could be before the invention of the telegraph. They tolerated all religions, and became the first empire to tolerate all three monotheistic religions under the same roof. They assimilated the civilizations they conquered, to the point of having architects, administrators and artisans from all over the world. They were not invincible, and in fact they were defeated by both Europeans and Muslims. But they were a formidable force that chastized the divisions in both Europe and the Middle East.
Drawn from sources of different countries, Chambers' book is a detailed history of what happened throughout those five generations.
Chambers merely tells a story. He does not speculate. It would be interesting to speculate too: why did this colossal empire contribute so little to the cultural world? why was there no great poet, painter, composer in the Mongol empire? And why did the Mongols feel so strong (at least for those five generations) to expand their empire as much as possible?