Reusing the "books" one could cause interferences when fixtures are
loaded in a very specific order such as:

https://buildkite.com/rails/rails/builds/76217#ee4ce591-e6c1-4a0d-a7db-1f83647d141e

Reproduction script:

```
activerecord $ bin/test -v --seed 23607 -n "/^(?:EagerAssociationTest#(?:test_preloading_a_regular_association_with_a_typo_through_a_polymorphic_association_still_raises)|ActiveRecord::Encryption::EncryptableFixtureTest#(?:test_fixtures_get_encrypted_automatically)|ViewWithoutPrimaryKeyTest#(?:test_attributes|test_reading))$/"
```