For now we show captcha in Book Library only for not registered users.
So e.g. you permit for not Registered user send review - we show to they Captcha.
If user registered we not show captch.
So you may Not permit add new review to book for not registered users.
for work with captha responsible file:
all places where and how we work with captch you may see if will check: "captcha_keystring"
The administrator has disabled public write access.