I found "The Roots of Obama's Range" to be a book that you can read easily in a short time, and which does make you think - a bit. But, it's nothing special.
As per his own account, Dinesh D'Souza started by trying to spot what was the ideology behind Obama's words and actions - was he a conventional liberal Democrat in the US sense, or even a socialist, or someone who saw himself as a sort of continuation of Martin Luther King Jr, etc? To me that was already a weakness in the book: D'Souza just assumes that Barack Obama will have a consistent ideology in his psyche, and the key to understand him, is to find out what exactly that ideology is - as if he was reading Obama's "software", so to speak. Well that may work for some people. It probably does work for Dinesh D'Souza himself, with his Christian-Reaganite ideology. It may even indeed work for Barack Obama - or it may not: would anyone get anywhere by trying to spot, say, Bill Clinton's or Richard Nixon's precise ideology? That D'Souza just assumes that that is the key to understanding Barack Obama tells a lot about D'Souza himself, that is, projection.
Anyway: Dinesh D'Souza does make an interesting case that what he calls the "neocolonial" ideology plays at least a significant role in shaping Obama's worldview. It would be even surprising if it didn't, given Obama's generation and background. The "neocolonial" ideology was - to some extent still is - taken for granted by most people of "intellectual" pretensions in Africa, Latin America, French and US universities, etc, especially in the 1970s. It is not even necessary to stretch to the breaking point - as D'Souza does - the evidence in Obama's book, "Dreams from my Father", and from the life of Obama's father himself. So my overall impression is that D'Souza is describing something that probably has some truth to it - but then exaggerating both its significance, and the evidence for it. One result is that the book can be very repetitive and it reads like it was written in a hurry. One indication is that, three times, D'Souza refers to Nicolas Sarkozy as France's prime minister, rather than as France's President. This is not trivial: it means either that Dinesh D'Souza is not aware that Nicolas Sarkozy is the president of France, rather than (just) the prime minister - which would suggest an "intellectual" of very limited interests and knowledge - and, or, that the book was not edited by anyone broadly knowledgeable. Either way, it made me skeptical of how much homework he does when writing his books.
Nevertheless, it remains an interesting read and it convinced me that there is probably something to his thesis, but not as much as he thinks.