There are some great novel recommendations here, but I wouldn’t say that most of them are lesser-known.
What are your recommendations?
As for me, I’ve exclusively read well-known novels, except if you consider someone like Alfred Bester obscure, for example.
One exception: Misha Burnett’s Endless Summer: Twelve Strange Tales of Mankind’s Future. It’s a collection of exceptionnaly well-crafted stories. It ain’t a novel, though.
I don’t know if Clifford D. Simak is lesser known, but his work is pretty foundational for a lot of more modern sci-fi. Before there was “I, Robot”, there was “City”. Before there were Ewoks, there was “Little Fuzzy”. Before there were living ships like in Farscape, Lexx, or Xenogenesis, there was “The Visitors”.
Clifford Simak didn’t write Little Fuzzy. That was H. Beam Piper.