Not to discourage any further answers but these posts about Medieval Africa from the FAQ on African history might be what you're looking for. There are also posts about ancient Africa (around the same time as Greece and Rome) but I don't think that's what you mean by the "kings and castles" period.

/u/Commustar wrote these answers:

How was the life of landed nobility in the Horn of Africa in the Middle Ages? What was the typical lifestyle of an Abyssinian nobleman or a Somali Adalite prince? (with /u/julyjuilletjulho)

What was going on in Nubia during the Middle Ages?

If a Western European at the beginning of the second millennium saw a typical city in West Africa, would it be familiar?

We hear a lot about the names Timbuktu and Swahili city-states, but less about the cities themselves. How important were urban centers in medieval and early modern sub-Saharan Africa?

How Muslim were the general populations of the Medieval Sahel Kingdoms (e.g. Ghana, Mali, Songhai, Kanem-Bornu) in comparison to the ruling class?

Did Central and South Africa develop powerful Empires (such as Ghana/Mali/Songhay in West Africa) during the middle ages and early modern period?

Here are other answers from other great flairs:

What did European Christians in the Middle Ages think of Ethiopia, and vice-versa? by /u/Compieuter

More below: