You are looking at a command called contribute

contribute {object} to {object}

Allows you to contribute to a book type object.

As you might have noticed, every bject can be considered a book if you feel like it.

You must be in the same location as both objects to use the contribute command.

Here is a little example:
create an elaborate novel
create chapter one
edit it
contribute it to the novel

You can read the novel (notice that read is a bit different to examine the novel).

Note: the read command will work no matter where the book is stored.
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