Does anyone know of book checkout data of libraries or purchase data of book stores that is (freely) available?

The data should have a connection between patron/customer and book.

So the only things I'd need would be: Patron/Customer identifier, ISBN(, date of purchase/checkout)

I want to try to build a book recommendation service. Once it's running, the plan is that it will generate its own data. But I would need some data to start with.

How would you go about this, if there is no publicly available data? I already searched Kaggle and Google Dataset Search but to no avail. I only found either patrons with only numbers of checkouts or books with numbers of checkouts, but no relation between the two.

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Data in German or English would be fine.

All help would be much appreciated.