I, too, am having the same issue. My booklibrary installation isn't new, though, but I have recently changed to PHP 7. When I select Settings Frontend, I get the error: "0  operator not supported for strings". I would like to adjust the frontend settings to prevent anyone from posting a review.
Please post the solution when you have found it. I will be happy to make the changes when you have figured it out. Thanks for the help.
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