\documentclass{book}

\usepackage{import}                 % To import an external document.
\usepackage[french]{babel}          % To help with hyphenation.
\usepackage{soul}                   % To provide nice hyphenation.
\usepackage{hyperref}               % To have hyperlinks to internet.
\usepackage{array}                  % To have better presentation in tables.
\usepackage{csquotes}               % To display quotes.
\usepackage{multirow}               % To have rowspan in tables.
\usepackage{makecell}               % To have colspan in tables.
\usepackage{tabulary}               % To make tables.
\usepackage{fontspec}               % To use local system fonts.
\usepackage{listings}               % To show source code.
\usepackage[dvipsnames]{xcolor}     % To define nice colors.
\usepackage[export]{adjustbox}      % To resize images.
\usepackage{graphicx}               % To import images.

\graphicspath{ {content/images/} }  % Where the images are
\lstdefinestyle{c-style}{}          % Define styles for each used source code language

\begin{document}
\import{content/}{aaa.tex}
\end{document}