\documentclass[a4paper,12pt,twoside,titlepage]{book}

\usepackage{scaladoc}

\ifpdf
    \pdfinfo {
        /Author   (Martin Odersky)
        /Title    (An Introduction to Scala)
        /Keywords (Scala)
        /Subject  ()
        /Creator  (TeX)
        /Producer (PDFLaTeX)
    }
\fi

\renewcommand{\doctitle}{An Introduction \\ to Scala}
\renewcommand{\docsubtitle}{\ }
\renewcommand{\docauthor}{Martin Odersky \\
Philippe Altherr \\
Vincent Cremet \\
Burak Emir \\ 
St\'ephane Micheloud \\
Nikolay Mihaylov \\
Michel Schinz \\
Erik Stenman \\
Matthias Zenger \\[25mm]\ }

\begin{document}
\frontmatter
\makedoctitle
\mainmatter
\end{document}