I find that most reviewers have based their evaluation on their agreement or disagreement with the ideas of the author. Although I liked many of his ideas, this book was very poorly written and contained very little new thinking, so I give it the rating it deserves.
Fanon doesn't state his idea and then support it, he just rambles on and beats around the bush and it's up to the reader to figure out what he's trying to say exactly. The result is that he uses a great many words to say very little. This makes for a very frustrating read.
The ideas he presents are not original either. Most of them can be found in Gandhi's "Hind Swaraj" (it's easy to download free English translations of this work off the internet and I stronlgy recommend reading it; plus it's much shorter than Fanon's book). Considering that "Hind Swaraj" was written almost 50 years earlier than "The Wretched of the Earth", the ideas Fanon presents were already old by the time he wrote the book!
Although Gandhi advocated non-violence while Fanon believes violence is inevitable in anti-colonial struggle, there isn't much that Fanon says that Gandhi hadn't already discussed. For instance, Fanon is often credited for predicting (or warning about) the fact that the intellectual and political elite of newly independent countries may simply replace the foreign oppressor. Gandhi had already warned his people about that, when he said that the leaders who overthrow colonialism by violence will also govern by violence. The example if India, which is one of the few colonies that gained independence by non-violence and which is one of the few that has been and remains democratic, proves that Gandhi's predictions were better than Fanon's since Gandhi also knew that violence was not inevitable in the fight for independence and that non-violence was the best way to avoid a simple substitution of the opressor.
In other words, if you want to read well-writen work and interesting ideas about anti-colonialism, don't waste your time with Fanon, read Gandhi instead...