Who is the richest country in Africa?

According to the Phillips Junior School Atlas which I read in school, Libya is the richest country in Africa. The reason for this is mainly due to its oil reserves, but most of North Africa, like Tunisia, Morocco and Egypt also have many Natural Resources which make them rich. Economically however, South Africa is probably Africa's richest country, but according to the book, it was classed as 'poor' or 'very poor'. There is no exact answer, this is just information which I learnt from the book I read.