Noted in pencil
The honest version: this site barely collects anything, because it has nothing to collect it for.
On this site
There is no account to make, no basket to fill, and no form to type into. The picker sorts books entirely inside your browser: the answers you click are used on that page and sent nowhere. The site keeps an aggregate tally of visits to see which shelves get read, with nothing in it that points at a person.
After you click a buy button
A buy button opens our retail partner in a new tab. From there their privacy notice applies, not this one, and whatever you do on their pages stays between you and them.
Back to the shelves
The books are the point; the paperwork just keeps the desk tidy.