A E Van Vogt can hardly be called unheard of, the null A series is quite a cult classic. But yeah, the Space Beagle is not his most well-known work.
It always surprises me (although it shouldn't) how many underrated gems there are still in the world. And new ones are produced every day.
E.G: I still think QTMN will deserve a place as a classic sci-fi author among the great ones, for "there is no antimemetics division" alone. And yet despite a solid fan following, it has never exploded in popularity. It is 10 times better than the 3 body problems, which comparatively had stratospheric success.
In movies, "Amelie" has been a planetary success, but from the same author, the excellent "The city of the lost children" is practically unknown.
Even last month, a tv show named "Nero" came out on Netflix, and while not revolutionary, is clearly above most of the crap that regularly comes out. Yet, nobody talks about it.
Popularity is a cruel mistress.