The traditional role of publishers was to filter out the dreck from what was worth reading, and to help promising authors improve their work via editor suggestions. That model will change with e-books.
I am sure that quite a bit of the above occurs. But it has become clear to me that another role for publishers has been to enforce progressive censorship. Certain thoughts are just not allowed in the dominant publishers. As an example, Robert Heinlien was not allowed to publish his science fiction classic "Red Planet" without registration and licensing of all personal weapons.
Yes, there are some small conservative publishers.
The Hunt for Red October caught fire on a fluke. Tom Clancy could not find a traditional publisher.
Our own Travis McGee (Mathew Bracken), despite a proved and successful self publishing track record, cannot find a traditional publisher.
I’ve been Reading the Eric Flint “1632” Ring of Fire series from Baen. I download the ePub format to my Mac, import it into the iTunes library, and sync it up to the iPad and read with iBooks app.