I realise the title wasn't clear enough so I've asked for an addition to it to make the question clearer.
I only added plain 'book' for those (ahem, stubborn

) people who want to insist on just saying book even when needing to distinguish from an ebook. For example, if such a person only reads ebooks then they might say, 'I don't read books anymore'. I hope that makes it clear how silly it would be to use simply 'book' to distinguish from 'ebook'.
This was mentioned in the OP, but now hopefully the title will make this clearer too.