I can only comment as a History teacher. Due to the country I live in there has tended to be a Eurocentric focus where Africa was included as an example of European imperialism in the 19th century. This may be in part due to the history of academia in Australia, and as Farida Fozdar and Catherine Ann Martin have pointed out, our History syllabus (especially in the junior years) still focuses on the history of our country (with an admittedly still largely Eurocentric focus). However, a recent syllabus revision in 2017 has seen the introduction of modern African history in the Year 11 Modern History syllabus called: "The Making of Modern South Africa". So there is an option for modern history teachers to offer this topic, suggesting small improvements in expanding our students' knowledge of other parts of the world.

As to why there aren't as many books published, a cursory glance at Google shopping for books covering this topic appears to show that they are being published, but not to the degree histories on modern European history are being released. This could be due to some following factors:

1. Writer's bias and Publishing bias. It could well be that scholars and writers may not be as interested in modern African history as modern European history for whatever reason they may have (cultural bias, etc where the focus would be on how South Africa related to European history). It could also well be that there isn't as much general interest in modern African history as a lot of the books on Google shopping tend to be either academic texts or school texts, so publishers don't publish as many books on the topic.
2. Access to primary and secondary sources. Sometimes access to sources is problematic for writers for a number of reasons. For example, the nature of the sources makes it difficult for historians and writers to reconstruct a detailed narrative as sometimes the primary sources have been lost or poorly kept making it difficult for extensive historical analysis. One example of this from my own country's history to illustrate this point is that during the period where the Australian government was removing Indigenous Australian children from their families, poor record-keeping took place, resulting in many of the survivours being unable to locate their biological families. Thus historians in this field don't have a complete data set to work from.

These are just two ideas that come to mind, but others would have a better idea.