This historical fiction novel covers this history of the a black family. How their ancestor started in Africa, was brought to America as a slave, and how the family fared under that despicable institution.
Alex Haley learned the stories of his family passed down along the generations to him. And using the details of the stories, researched for more, and from that wrote this novel.
The visceral emotions evoked were probably due to feeling connected to it. Over the past couple years I have researched my own genealogy. That came about after taking a DNA test and realizing I could use suggested relatives to find more information. But, Kunta Kinte, the Haley ancestor knew his grandfather was from the same part of Africa as my Y-DNA has the highest concentration (suggesting the origin location). Reading Roots feels like what my story could be if only I could find the same information.
I suspect this is why the show captured the American imagination.