Infinite Jest by David Foster Wallace (1996) has an interesting structure using hundreds of footnotes some of which have themselves footnotes. The ending is not

Infinite Jest by David Foster Wallace (1996) has an interesting structure using hundreds of footnotes some of which have themselves footnotes. The ending is not straightforward and the novel's chronology non-lineal. It contains disgressions on many topics. According to the Wikipedia, in an interview Wallace mentioned that the plotting and notes have a fractal structure modeled after the Sierpiński gasket, suggesting some degree of recursion.