I am reputed among some as having an extraordinary memory. This is not true. Such feats as being able to give the history, say, of the formation of the Christian canon off the top of one's head are the result of reading many different books about the topic. It's all about building cognitive structures and associative links.
My knowledge about African history is extremely limited except for the early history of North Africa concerning the Egyptians, Phoenicians, Persians, Greeks and Romans. It's not that I've never read about sub-Saharan or modern Africa, it's just that I've not read enough and what I have read hasn't been well integrated conceptually. Pick up a book on a particular area or period and I often find a lot that is familiar from other readings and the occasional documentary, but without such a prompt I'm usually at a loss.
Additionally, as regards Africa, too much of what I've read is from a European perspective: explorations and exploitations as it were.
This book is of the exploration/exploitation kind supplemented by some geography--much like Mooreheads White and Blue Nile books. Along with the latterly-read King Leopold's Ghost, it serves as a beginning for learning about the region and its people, but I have far, far to go...
Dad, however, does have an excellent, albeit perverse, memory. I recall that once, in a discussion of the film High Noon, he noted that he first saw it at such-and-such a theatre at such-and-such a date. Stopping him, I asked how it was possible for him to remember the date so exactly. Reflecting a moment, he said that it was easy because he had purchased such-and-such a car just the day before. This struck him as a sufficient explanation.