Various people have claimed that all of literature has only a limited number of plots. Here's a FAQ with several of the classifications people have come up with:
http://www.ipl.org/ref/QUE/FARQ/plotFARQ.html
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Cap'n Q
The most merciful thing in the world, I think, is the inability of the
human mind to correlate all of its contents. We live on a placid
island of ignorance in the midst of black seas of infinity, and it was
not meant that we should go far. -- HP Lovecraft