allow book-style navigation block below content - show siblings

Issue Summary

hi,

in order to fully replace the book module I would need the last missing piece of the book navigation below content.

we have
- the parent node is in the breadcrumb
- any child nodes can be shown using the integrated "children view"

missing
- siblings to the current node and a way to navigate in a kind of "back to preceding" and "next to following" relative to the current node

It seems that this cannot be done with the currently available options in the views integration?

any ideas?

thank you!