\documentclass[]{book}%

\usepackage{gcheck}

\usepackage[a6paper,twoside]{geometry}
\geometry{dvips,showframe}

\begin{document}

\typeout{}
\dcheck\paperwidth{298.75394pt}
\dcheck\paperheight{423.94606pt}
\dcheck\textwidth{209.12683pt}
\dcheck\textheight{296.76094pt}
\dcheck\oddsidemargin{-36.41916pt}
\dcheck\evensidemargin{-18.49371pt}
\dcheck\topmargin{-51.46346pt}
\dcheck\headheight{12.0pt}
\dcheck\headsep{18.06749pt}
\dcheck\footskip{25.29494pt}
\dcheck\marginparwidth{125.0pt}
\dcheck\marginparsep{7.0pt}
\dcheck\columnsep{10pt}
\dcheck\hoffset{0pt}
\dcheck\voffset{0pt}
\ccheck\mag{1000}
\checkresults
\typeout{}

\manyfoxes\manyfoxes\manyfoxes
\end{document}
