In his preface, historian D.T. Niane (who is credited as the author of the book) explains his sources. He attributes the version of the story he tells to "an obscure griot from the village of Djeliba Koro."
As he explains, griots in the present day work as professional African musicians, but in the day of medieval Africa, they were incredibly important figures. They were counselors to rulers, preservers of constitutions and laws, tutors to princes, and markers of tradition. In short, they were integral to medieval West African tribes and empires. He then points out that the tradition of griots does persist in those areas today.
Niane then addresses the Western tendency to "scorn oral sources" as unreliable. Since griots carry on history through performance and song, rather than written document, they are often seen as inferior sources. But Niane describes how, for griots, "all true learning should be a secret." They travel amongst their people, learning traditions and showing restraint about what should be shared with whom. It is an utterly distinct way of preserving tradition, and cannot be understood by Western standards of written history.
Niane ends his preface by offering that his eyes have been opened through his travels, and hopes that his relation of this epic tale will do the same for other readers.
Niane's preface is useful in setting up the reader's expectation and understanding of the griot as integral to Mali - which does not refer solely to position in the caste system (which the griot himself will stress in various ways through the epic itself). More than that, understanding the importance of the griot will help the reader to explore the central themes of memory, history, and tradition.
As Niane points out, the griots were expected to preserve law and tradition through their remembrances and history songs. Without the fulfillment of their duties, kings could not be counted on to remember their own constitutions, laws and precedents. The very stability of society relied in part on their living documents. The epic that follows is itself a griot's song transcribed by Niane, and its messages of peace, understanding, heroism and duty are in part meant to remind a listening audience of Mali's virtues, not just to relate a history.
Heroism will be defined several times in the epic as that which engenders remembrance. Niane takes the time in his preface to drive home that this act of remembrance is dependant on the work of the griots who are trained for their duty as keepers of history.