What do you want to know? There is a wealth of literature out there. Start with a general survey book like Martin Meredith's The Fate of Africa (though outside the US it might be called the State of Africa), it kinda sums up those regimes (plus Africa as a whole), the Derg/Mengistu Ethiopia more than the others.
The most general thing I can say is that they were all abject failures, laughable as experiments in statecraft much less communism. When Frelimo might be the best among a group of things, you know that group has serious issues.