I have read the book, met the author and will be writing a review soon. In the book Steven Radelet makes the important point that African countries are not born equal. About half of sub-Saharan African countries have, since the mid 1990s, have shown signs of preconditions for take off. The stars in the book are the usual suspects, Ghana, Mauritius, Botswana. The suckers are mostly Sahelian and central African.
An abbreviated version of the book appears in the Journal of Democracy.