Bookmind collects no data. Bookmind has no cloud, it *cannot* store data.
Your reading history and book collection are stored only on your device. If you enable iCloud support for the app, Apple does store that information, but only to sync with your other devices.
Bookmind uses Open Library to fetch book and author details. We must send a header with each request that identifies the app and version, but otherwise send nothing beyond the standard device and os information Apple already sends. Refer to https://openlibrary.org and https://archive.org/about/terms.php for more details.
If you opt in to share analytics and crash data, Apple will store anonymized usage and crash reports. This data is used only to improve Bookmind, it is not shared with anyone.
Emails to customer support are retained only as long as it takes to resolve the issue.