Exactly what Ken said. Look at the documentation for org-latex-classes to
see the full description. You can see an example in my Emacs config:
https://github.com/zzamboni/dot-emacs/blob/master/init.org#various-exporters
(look
for the paragraph that starts with "Some customizations for the LaTeX
exporter"). Once that is defined, you can specify the name you used as the
value of "#+latex_class:" at the top of your org file, e.g.:

#+latex_class: book-no-parts

Best,
--Diego


On Wed, Nov 28, 2018 at 8:57 PM Ken Mankoff <mankoff@gmail.com> wrote:

> Hi Bill,
> On 2018-11-28 at 20:42 +0100, William Denton <wtd@pobox.com> wrote:
> > Is there a way, exporting as a book, to make Org skip "part" and make
> > a top-level Org headline turn into a chapter? Is there a built-in way,
> > or do I need to make my own class in org-latex-classes that has the
> > structure I want?
>
> What about customizing org-latex-classes?
>
> It contains:
>
>  ("book" "\\documentclass[11pt]{book}"
>   ("\\part{%s}" . "\\part*{%s}")
>   ("\\chapter{%s}" . "\\chapter*{%s}")
>   ("\\section{%s}" . "\\section*{%s}")
>   ("\\subsection{%s}" . "\\subsection*{%s}")
>   ("\\subsubsection{%s}" . "\\subsubsection*{%s}")))
>
> Seems like modifying that could provide the behavior you're looking for.
>
>   -k.
>
>