Show child pages in parent node view details in a book I'm using the Book module to maintain the parent-child relationship between content. I want to see all child pages expanded when I see a parent node details page.
How can I achieve it?

I tried with THEMENAME_preprocess_book_tree(), but so far I have not been able to achieve that I wanted.
Is this the right hook to use in my case?
I managed to find a solution. I would like to post it here if somebody looking for similar solutions.

Make a view for the parent page with all needed configurations. In my case, I have the main chapter page as the parent, the content type is 'chapter'. And when I see the view in a page I want to see all subchapters coming under it. The further steps are followed:


Browse to /admin/structure/views and click on "Add view".
Enter a view  name, Select content type from view settings
Check the "Create a block" checkbox only. Then click on
"Save &amp; edit".
On the right-hand side, click on "Advanced" so that the advanced
menu appears.
Click on "add" next to "Relationships" to add a relationship.
Select "1st parent" (the parent book node) and click on "Apply and
configure relationships".
Check the "Require this relationship" checkbox and click on "Apply".
Click on "add" next to "Contextual filters" to add a contextual
filter.
Select "ID" (The node ID) and click on "Add and configure contextual
filters". Choose relationship to "Book 1st Parent"
In the "when the filter value is not available" section, select
 "Provide default value" and in the "Type" drop-down menu, select
 "Content ID from URL"
click on "Apply" &amp; Save the view
Place the just created block in the page by visiting structure >
 block layout