I quite enjoyed reading Fiftieth Gate, and I don't find its concepts all that complicated...but that might just be a result of my teacher's excellent tutelage.^^
Basically the Fiftieth Gate refers to this concept of Jewish mysticism, whereby there are 49 gates separating "good from evil, the darkness from the light," and you have to symbollically "pass through" these gates before you can achieve the enlightenment which awaits at the last gate. The chapters are fragmentary because every gate is an experience within itself, and must be understood one by one which will then determine what state will be achieved by the Fiftieth Gate -- either a void of knowledge and feeling or a state of complete knowledge which transcends physical and concrete boundaries.
Practice question: Analyse ways in which history and memory generate compelling and unexpected insights.