Is Nick Carraway’s failed romance with Jordan Baker a subplot in the Great Gatsby or is it part of the main plot? You could argue that anything that comes from Nick’s presence in that book is separate from the plot, except that it’s all integral.
Finnegans Wake
Stephen King’s “Misery” is pretty much sub-plot free. I guess it depends on how closely “sub-plot” is defined. Annie Wilkes’ backstory is discussed, but I wouldn’t call that a sub-plot. Excellent book, by the way.
Flowers For Algernon, the full-length novel version, I don’t think it has any subplots at all. Just a straight story told from the perspective of the main character. Unless you count different things he does, goes through, experiences, etc, as subplots, it’s all just one plot.
It’s also hard to say when you have a whole BUNCH of plots that come together in one giant way. For example, Dune, you could argue, doesn’t even have a main plot, but just a bunch of sub-plots that all end up coalescing.
Isn’t that just one big plot, though? It’s basically the story of this kid as he lives three(?) days of his life, and everything that he does or thinks about during that time, isn’t it?
(I should say it’s been a while since I’ve read it. :))
“There’s this guy, and he does some stuff” isn’t really a plot, though. If it were then almost any novel told from the perspective of one character would be a novel without subplots. Again though, without a strict definition of “subplot” this question is impossible to answer.