First, copy the slug from your books showcase URL

Now, go to WBG Books -> General Settings and find Gallery Page Slug option.

Paste the slug and save settings.
Now you should see back button in your books details page
First, copy the slug from your books showcase URL

Now, go to WBG Books -> General Settings and find Gallery Page Slug option.

Paste the slug and save settings.
Now you should see back button in your books details page