theducks is quite right about the Check titlecase function. Though it does have one limitation currently in comparison to what you are asking for, in that it only checks the titles of books, it does not look at authors.
So the question becomes whether (a) you accept that the Check titlecase function is sufficient to stop tearing your hair out when it comes to book titles
and then (b) if the plugin allowed you to check authors as well whether that would complete the coverage you are after.
I am reluctant to add specific checks for "All lower", "All upper" etc as these are really just permutations of the same thing - what would you do with a title that was all lowercase? You would rename it (most likely) to use titlecase.
So if making available an option to check titlecase to the Authors is useful that is something I would consider.