For deny review in Book library for every book - you need close that possibility in Book library settings.
Clear all review you may with help review manager - in Booklibrary or with help database.
Also with help Database - you may remove all data from Booklibrary.
All tables for book library have prefix: booklibrary
Also you may remove all data - reinstall Book library component.
For Mass data import/export - best use import export features - what now exist in Book library software