I am not sure about the exams and what kind of questions they ask but in general The Human Cycle gives a good glimpse of mankind’s march through history and The Renaissance of India provides a strong foundation to understand India. In terms of literature, Early Cultural Writings and the Future Poetry give us a very good glimpse. On the other hand The Life Divine and Savitri remain his main, most important works. But if one wants to read in some kind of a summary way the basic philosophy and metaphysics of Sri Aurobindo’s thought then The Letters on Yoga volume One and Two should suffice.
Affectionately,
Alok Da