You can define a partwithabstract
environment:
\documentclass[oneside]{book}
\usepackage{xpatch}
\makeatletter
\xpatchcmd{\part}{\null\vfil}{\vspace*{.1\textheight}}{}{}
\providecommand{\abstractname}{Abstract}
\newenvironment{partwithabstract}
{\begingroup\let\@endpart\relax\part@withabstract}
{\endquotation\endgroup\@endpart}
\newcommand{\part@withabstract}{\@dblarg\part@@withabstract}
\def\part@@withabstract[#1]#2{%
\part[#1]{#2}%
\vfil
\begin{center}\bfseries\abstractname\vspace{-.5em}\vspace{\z@}\end{center}
\quotation
}
\makeatother
\usepackage{lipsum}
\begin{document}
\tableofcontents
\begin{partwithabstract}{First Part}
\lipsum[1-2]
\end{partwithabstract}
\begin{partwithabstract}[Second for the TOC]{Second Part}
\lipsum[2]
\end{partwithabstract}
\end{document}

The main change is that the title is set at a fixed height from the top; the abstract is vertically centered in the remaining space (it's your responsibility to make it fit).
If you change \vfil
into \vfill
in the definition of \part@@withabstract
, that is, do
\def\part@@withabstract[#1]#2{%
\part[#1]{#2}%
\vfill
\begin{center}\bfseries\abstractname\vspace{-.5em}\vspace{\z@}\end{center}
\quotation
}
the abstract will be flush with the bottom margin.

You can remove the \abstractname
related bit, if you so prefer: the code to remove is
\begin{center}\bfseries\abstractname\vspace{-.5em}\vspace{\z@}\end{center}
Technical note I used oneside
just for showing the two part pages side by side.
book.cls
does not haveabstract
at all. With some modification it is possible to use thearticle
version ofabstract
and 'inject' it into\part
\part
. So can use something like\setpartpreamble{\begin{quote}Blabla\end{quote}}
.scrbook
is a book class and you don't have specified a class. This is one reason for the MWE that you always should add to the question and for correct markdown. BTW:scrbook
has an option to emulate standard classbook
.