How to get book field values?

Unfortunately, there has been no response to this support request. I updated the title to English.

Timely responses to support requests in the Drupal core issue queue are rare. There are better forums for questions such a slack or stack exchange. I encourage you to try them.

try this
{{ node.getParentNode().field_gold.value }}

@acakyra, you can use something like this.

{% if node.isTranslation %}
{% set parentNode = node.getTranslation(node.source.langcode) %}
{% else %}
{% set parentNode = node %}
{% endif %}

{% if parentNode.field_gold %}
{{ parentNode.field_gold.value }}
{% endif %}

And Thank You.

@acakyra is there anything else you need from this if it can be closed out?

I am closing this issue due to inactivity. Reopen it as necessary.