If you're trying to present as complicated a historical phenomenon as decolonization as a whole, you have two basic options: to try to talk about it in general, in terms of general trends or patterns; or though a few cases, from which you allow the reader to generalize. Shipway tries to split the difference, presenting general patterns using a fairly large number of cases. This is perhaps a good approach, but the results are somewhat mixed; how successful they are probably depends to some extent on the audience. Shipway manages to cover a lot of ground quickly by communicating a great deal through historical allusion. For my class of undergraduates, who did not have much of the background, large parts of he text were more or less unintelligible. This is maybe just a way of saying that it's not an introductory text-- which it does not, in fairness, claim to be. But nor should it be true that the reader has to know a great deal about each of the cases in order to make sense of the comparisons between them.