It's a typical travel adventure by Jules Verne, but not as good as usual. It is sometimes almost boring with lots of descriptions of the accomplishments of the European explorers of Africa. It is, nevertheless, a good example of the evolution of western morals -- a progressive and humanist work when it was written, most of it would be considered racist and misogynist today.

The plot has a flaw [SPOILER]: placing a piece of metal in the compass of the ship wouldn't have the effect described. The compass would have a fixed azimuth and one of two situations would happen: either it was the desired azimuth and the ship would continue its way as if nothing happened, or it wasn't and the ship would go in circles as the pilot tried to adjust (and would soon find out that something was wrong with the compass).