Definitely a unique approach to philosophy, thoroughly reformed and presuppositional. Gangadean's reflections on the Problem of Evil I found especially helpful. If we as Christians believe that the root of all evil is unbelief in God, then for the unbeliever to claim that they cannot believe in God because of evil becomes circular; they cannot believe because of their unbelief.
Gangadean's Epistemology, it seems, needs more clarification (ironically). He argues that basic truths (that is core truths of one's worldview like whether or not God exists) must be clear to reason. But it seems unclear to me what exactly this entails. This can quickly be reduced to hard rationalism where every truth is deducible from a set of axioms, but this does not seem to be Gangadean's intention. It seems to me that Gangadean, like many presuppositionalists, is thinking of worldviews as a web or a system of beliefs, where there is a core of interlocking strands that is more crucial to the structure of the web than its outer edges, even though every strand plays an important role in upholding the system. At the same time, some strands can be exchanged for others without changing the structure of the web while the central strands cannot be exchanged. As a result, while the more basic truths are clear to reason, not every truth is this way (e.g. quantum physics, the law and force of gravity etc.). This is a promising approach but there are certain epistemical issues that Gangadean simply dismisses, like the Gettier dilemma's, which seem to demand more of a robust response.
For Gangadean, it is crucial that certain basic truths be clear to reason if people are to be held culpable for unbelief. But, Gangadean is not a Van Tillian. He does not believe that each person knows whether or not they admit it. Rather, he argues that every person should know or has the ability to know God. Every action is based upon a belief or a claim to know the good. No person can act knowing and willing evil. Even the most insane sociopath acts in the belief that his happiness is the highest good and is achieved through other people's suffering.
Coming from a Reformed perspective myself I find this approach powerful, even though I think some of Gangadean's arguments fall short or need further explanation. Then again, Gangadean's purpose for this book is not to give a comprehensive philosophy but only to establish that, "the basic things about God and man and good and evil are clear to reason." Romans 1 by itself compels me to agree with him.