Re: What should the relation between \book / \bookpart be?

Hi David,

I’m afraid I don’t follow all of your writing, probably because I don’t 
have an understanding of how/why an “amended copy” of a \book {} would 
be used, as in

On 07/08/2026 15:45, David Kastrup wrote:
> bookA = \book { ... }
> bookB = \bookpart { ... }
>
> \book { \bookA ... }
>
> which would mean to create a book as an amended copy of \bookA

In my understanding, there is or should be a direct relation between 
\book{} statements and output files. One \book{} statement can 
correspond to 0 or 1 output files per backend/output file format, but 
never two. Allowing syntax like

\book { \book {} }

or

\book {
   \book {}
   \book {}
}

would not make sense based on that direct relation and only lead to 
confusion. Am I wrong? Is there ever a use case that would necessitate 
nested \book{} environments?

Hence I would strongly lean toward this:

On 07/08/2026 20:21, David Kastrup wrote:
> [Possibility 1:] a book or bookpart gets stamped at creation
> for being one or the other depending on whether it is done using \book
> or \bookpart.  This is sticky and determines the allowable use.

Having a hard and fast rule here creates clarity and leads users toward 
structuring their projects in an understandable and useful way.

On 07/08/2026 15:45, David Kastrup wrote:
> For rearranging an existing source into something that is only a part of
> a larger document, the current relative fluidity between book and
> bookpart may be convenient.

It may be convenient, but allows for tangled up projects that are hard 
to understand and maintain.

Best, Simon