The basic message of the book is very simple: the Western Sahara is illegally occupied by Morocco. A slew of international statements (the 1975 ICJ ruling, the 2002 Opinion of UN Legal Counsel Hans Corell, and repeated UN Security Council and General Assembly resolutions) make that absolutely clear, and yet the international community remains tolerant of this massive breach of international law - a friend pointed out to me the other day that the Western Sahara is the largest single area of disputed territory on the planet (leaving aside the peculiar situation of Antarctica).
The authors do differ among each other, on the precise role and responsibilities of the international actors - the UN, Spain, and the European Union - which has disgracefully colluded with the theft of Western Sahara's natural resources (particularly its rich fishing grounds). But the basic message is consistent: Morocco and its collaborators are behaving illegally, and not a single country in the world recognises Morocco's annexation of the Western Sahara.
Declaration of interest: I'm working with the Frente Polisario to assist them in the liberation of their country, and I'm proud to do so.