My Latex Template for Kindle (Or IPAD)

template.tex

\documentclass[8pt]{memoir} 
\usepackage[utf8]{inputenc}
\usepackage[paperwidth=9cm, paperheight=11.5cm, top=0.5cm, left=0.5cm, right=0.5cm, bottom=0.5cm]{geometry}
\usepackage{graphicx}
\usepackage{tikz, blindtext}

\makechapterstyle{box}{
  \renewcommand*{\printchaptername}{}
  \renewcommand*{\chapnumfont}{\normalfont\sffamily\huge\bfseries}
  \renewcommand*{\printchapternum}{
    \flushright
    \begin{tikzpicture}
      \draw[fill,color=black] (0,0) rectangle (2cm,2cm);
      \draw[color=white] (1cm,1cm) node { \chapnumfont\thechapter };
    \end{tikzpicture}
  }
  \renewcommand*{\chaptitlefont}{\normalfont\sffamily\Huge\bfseries}
  \renewcommand*{\printchaptertitle}[1]{\flushright\chaptitlefont##1}
}

%Begin Decorative packages
\usepackage{type1cm}
\usepackage{lettrine}
%End decorative packages

\usepackage[T1]{fontenc}
\usepackage[scaled]{helvet}
\renewcommand*\familydefault{\sfdefault}

\frenchspacing
\sloppy
\pagestyle{empty}

\chapterstyle{box}
\begin{document}

\title{Latex Template for Kindle}
\author{by YOUR NAME}
\date{}
\maketitle
\newpage

\newpage
\chapter{Preface}{}

\lettrine[lines=3,slope=4pt,findent=-3pt]{O}{nce upon} a time, lala lala lalala lalalala. 

\newpage
\chapter{Introduction}

\lettrine[lines=3,slope=4pt,findent=-3pt]{O}{nce upon} a time, lala lala lalala lalalala. 

\end{document}