The book is very good and easy to read (includes maps and a good index). It is true that the author only shows some aspects of its subject matter (mostly european discovery, conquest and colonisation) and thus the book may be considered a bit limited in its scope, but otherwise it would have probably missed the target becoming a tedious scholarly volume. Nevertheless it is a very interesting introduction to the area and gives a good insight of the way the french and the british faced and handled their imperial aspirations.
I also strongly reccomend the excellent book on the River Congo by Peter Forbath, which follows a similar pattern and which will help you complete a vast panorama on West Africa.
From Amazon.com
Wonderful
A wonderfully readable history of the Niger River, and the fascinating personalities that made that history.