Setting KOMA-Script document in half legal paper

I need to resize a letter sized document into a page with a half legal paper size. I'm using KOMA-Script class scrbook, but I can't get it using typarea. Surelly I'm doing something wrong. I read this post before ask. This is my MWE:

\documentclass[headings=big,bibliography=totoc]{scrbook}
\begin{document}
\frontmatter
\subject{Thesis}
\title{Vertical borderline}
\author{Me}
\date{\today}
\maketitle
\end{document}


What I need is a document with a half legal sheet page, for print two pages over a legal sized sheet of paper. Suggestions?

• paper=7cm:9cm should do*. Use it after bibliography=totoc. * Substitute real dimensions. EDIT: You gotta move all the options from typearea to the options of documentclass. – Johannes_B Aug 17 '16 at 6:23

With the following MWE you get an document with landscape, half legal size with KOMA-Script class scrbook based on your given code. See the important code changings marked with <========.

\documentclass[%
bibliography=totoc,
footinclude=false, % <================================================
% paper=21.6cm:35.6cm, % Legal   8 1⁄2 × 14 inch    216 × 356 mm
paper=10.8cm:17.8cm, % legal/2 landscape  paper=width:heigth <========
paper=landscape, % <==================================================
DIV=10           % <==================================================
]{scrbook}

%\areaset{10cm}{17cm} % {width}{height} <==================== without DIV
\usepackage{showframe} % <=========================== to show typing area

\begin{document}

\frontmatter
\subject{Thesis}
\title{Vertical borderline}
\author{Me}
\date{\today}
\maketitle

Text text text text text % <================================ for 2nd page

\end{document}


with the resulting pdf:

Please see that the current version of KOMA-Script uses paper=width:height instead in earlier versions paper=height:width. Please see my comments in the given MWE.