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 really enjoy Hal Clement’s Mission of Gravity (1954) and the sequel Star Light (1971). The worldbuilding is really good, and it gives new a similar feeling of wonder as Clarke’s Rendezvous With Rama (1973) and Larry Niven’s Ringworld (1970).