\documentclass{book}
\usepackage[fleqn]{amsmath}
\usepackage{amssymb}
\usepackage{alltt}
\usepackage{latexsym}
\usepackage{makeidx}
\usepackage{textcomp}

\usepackage{buch}          % eigenes Zeug

\makeindex
\begin{document}

\include{Text/preface}
\tableofcontents
\newpage
\include{Text/kap1}
\include{Text/kap2}
...
\include{Text/kap19}
\printindex
\end{document}
