As far as the book itself is concerned, this is a reasonably engrossing story. There's too much dialogue filling in historical information that makes the flow awkward. The story definitely loses momentum toward the end, as very little of interest happens in the final chapters compared with what has come before.
Also, despite what you read within the pages, this story has little or no historical value. It certainly does not represent a historically accurate picture of Haley's family tree, despite what he says about his "research" and his journey to Africa. Tragically, the black experience has ensured that the kind of genealogical information we crave is irretrievable. That does not excuse Haley's sloppy work and false claims, however. Unfortunately, this book also contains much plagiarism of "The African" by Harold Courlander, as has been known since a lawsuit related to it in the 1970s.
Harold Courlander's novel, from which Alex Haley stole, is justly neglected - Haley's novel could justly be neglected too. It's a good read, but not an essential or important one. When you consider the baggage that it carries, one should look elsewhere for a definitive novel about the black experience. Maybe "The Book of Negroes" by Lawrence Hill?