starshipcat explores the har-dee-har-har "Let's type up a classic, put another name on, and see if this crap would sell/how ignorant those editors are"--and the notion of classics in science fiction,
here.
This brings up such a good question: just what is a classic? (Other than the "classic means the works of Ancient Greece and Rome.")
My own simple I-have-a-headache definition is, a book that has not only endured over time, but rewards rereading.