But how can unknown publishers be judged, like those unconnected with any top universities?
There are no rankings of publishers I'm aware of (what criteria would you even use?); however, my experience is that academics also barely care about the prestige of the publisher. If there are any publishers at all whose names carry weight, it's CUP and OUP.
Just make sure not to publish with a predatory publisher and you should be set.
I suspect this varies a lot by field. In philosophy it does matter where one publishes; a 2013 poll on a philosophy blog gave the top 7 English-language publishers as:
- Oxford University Press
- Cambridge University Press
- Harvard University Press
- Routledge (Taylor & Francis)
- Princeton University Press
- MIT Press
In my subfield, due to the closer connections with mathematics and computer science, a lot of good volumes come out with Springer, which is nowhere near the top of this list. So even knowing the field is not sufficient to be able to determine what the best publishers are.
As with most questions of this sort, you are probably best off consulting senior members of your field, and seeing where the stars of your field publish.
I would look at the portfolio of the publisher: are there any/enough books in there on a comparable topic and level as the manuscript I want to publish?
for journals: journals have a number that is drived by the sitations of their articles. I don't remember the name. it is something with factor or impact. you can check journals' reputation of the publisher. also, I would recommend you to read fiew articles on the journal and if you find it quality. you should think publishing in there. I think that we need quality papers in every journal and one way to do that is to publish in less known journals or publishers in general.