The starting point I'd recommend is John Spencer, _Language in
Africa_, Cambridge University Press, 1963. This is dated but still a
good place to start. _Current Trends in Linguistics: Linguistics in
Sub-Saharan Africa_ (Mouton) is contains useful material.
One of the best single-country studies is _Language in Ethiopia_, edited
by M.L. Bender et al. and published by Oxford University Press (1976).
It includes linguistic, socio-linguistic, education, and policy
chapters.
Also, Eyamba Bokamba, at the University of Illinois, has done some
more recent work relative to Zaire and central Africa, and Wilfred
Whiteley did some classic studies on language policy in East Africa.
Unfortunately, I don't have any of those titles handy.
Herb Stahlke
Ball State University