You can request your data here https://www.goodreads.com/user/edit?ref=nav_profile_settings

They will send a confirmation email. After you click the link to confirm, it says "We will provide your information to you as soon as we can. Usually, this should take no more than a month."

EDIT: you can export your book database as CSV (shelves, ratings, reviews, etc) here https://www.goodreads.com/review/import (there's a link towards the top to export...disregard that the URL says "import".