Despite its relative age - it was first published in 1990 - this is a good starting point and a rather excellent introduction to the Mongols. The book is divided into four biographies, those of Genghis Khan, of his grandsons Kubilai Khan, who conquered China, and Hulegu, who conquered Iran, put an end to the Abbasid caliphate and sacked and destroyed Bagdad, and Tamerlane.
Each of the chapters has roughly the same size (40 to 45 pages) and can be read separately. Each also starts with the warlords main claim to fame, before telling the story of his life and wars and finishing with an assessment of their achievements and their respective legacies. Finally, each section also includes a genealogical table, listing the warlord's descendants and successors in particular. Also included in each chapter are sections of the respective armies, their arms and equipment, and the main battles that they fought under each of the warlords.
Note also than fans of Conn Inggulden's series on Genghis and Kubilai Khan (and which also include Hulegu) will also benefit from reading this book and using it to provide background information. One limitation, however, is that, given the book's relative age, the bibliography is not up to date.
Finally, there are the rather superb plates by Richard Hook, four for each chapter, and a no less superb collection of photos, maps and illustrations.
Still worth four stars.