I must have mentally parsed the “unknown” used by OP as “not widely known” (to the HN crowd), and if you look at a lot of the contributions, many of the authors are not exactly “unknown” either.
Fair enough. Very specifically I think that book is pretty standard reading for anyone interested in epistemology of science - but that doesn't mean it is generally known.
I read the original as looking for books that are good in subject X, but not well known in that subject area.
I must have mentally parsed the “unknown” used by OP as “not widely known” (to the HN crowd), and if you look at a lot of the contributions, many of the authors are not exactly “unknown” either.