For books that are already live on MBR, your rating will go live immediately, and you can change it at any time.
For books not yet on our site, we check the links and make sure all the book information is correctly filled out before posting. That can take anywhere for a few minutes for books submitted by authors (who are asked to fill out more information) to several hours for books readers submit. It depends on how many books submitted and what else we are doing behind the scenes. We're all volunteers here, so be patient. We promise to get it posted as soon as possible.
Thank you for your support!