How to show book block only if node is in a book?

Hi,

I'm trying to configure "context sensitive" book menu blocks, one per book or "topic", to allow navigation inside the Drupal books. Those book menu blocks are not supposed to be a primary site navigation.

In some cases, I can make this work by limiting the block visibility by path, or by content type. However, in (too) many cases the book menu block is always visible, even if the current node is not even in any book.

I believe, this is not a very exotic use case for the 'Menu block' module, so probably there is a way to make book menu blocks visible only if the current node actually is in a book. However, I can not find such an setting, so I'm kindly asking for help.

If such an option is missing, I'd suggest to change this issue into a feature request.

Thank you!