Combine custom titlepage with \extratitle in scrbook

Question

I am using scrbook and I have the following problem: I need a titlepage on page 3 and an extra titlepage (a bastard title/Schmutztitel) on page 1. The following example almost does what I want:

\documentclass[twoside, a5paper]{scrbook}
\usepackage[utf8]{inputenc}


\begin{document}
\author{The Author}
\title{Book Title}
\extratitle{The Author\\ Book Title
}
\lowertitleback{ISBN XXX}
\maketitle
\tableofcontents
\section{First section}
some text
\end{document}

Now my problem is that I want the author above the title (and the date at the very bottom of the title page). So I probably have to customize my titlepage with a

\begin{titlepage} ... \end{titlepage}

environment. But if I try to include this instead of \maketitle, the bastard title on page 1 vanishes:

\documentclass[twoside, a5paper]{scrbook}
\usepackage[utf8]{inputenc}


\begin{document}
\author{The Author}
\title{Book Title}
\extratitle{The Author\\ Book Title
}
\lowertitleback{ISBN XXX}
\begin{titlepage}
bla
\end{titlepage}
\tableofcontents
\section{First section}
some text
\end{document}

Answer 1

Use another titlepage environment for the bastard title:

\documentclass[twoside, a5paper]{scrbook}
\usepackage[utf8]{inputenc}

\begin{document}

\begin{titlepage}
  \raggedright
  The Author\\ Book Title
\end{titlepage}

\begin{titlepage}
bla
\end{titlepage}

\thispagestyle{empty}
\null\vfill
{\raggedright
  ISBN XXX
}

\tableofcontents
\section{First section}
some text
\end{document}