Very good question! Not an IP lawyer, but I believe the gist of it you may copy the original work, but not any sufficiently transformative derivative work, as that would gain its own copyright. So you could copy the text of a public domain book and re-publish it yourself, yes. You could also sell your copies for $10/ea, just like the publisher you're copying from is doing, or give them away for free, or whatever you like.

The tricky bit is what its "sufficiently transformative" to gets its own copyright. Probably simply text printed in a book is not, so I think you'd be OK scanning and distributing such a book. But if the publisher added new footnotes or illustrations or cover art or a forward, etc, that would still be covered under its own copyright and you would have to remove them. And I could see an argument that a certain printing style (maybe a choice in font or page layout?) could be transformative, but I think that starts to be quite a stretch.