vimtex/test/examples/book-multifile/main.tex

\documentclass{book}

\input{preamble}
\bibliography{book.bib}

\begin{document}

\frontmatter
\input{ frontmatter }

\mainmatter
\input{chapters}

\appendix
\input{appendix}

\backmatter
\input{backmatter}

\end{document}