%
%------------------------------------------------------------------------------------------------------------------------ %
\documentclass[english,11pt]{book}
%------------------------------------------------------------------------------------------------------------------------ %
\usepackage[fleqn]{amsmath} %
\usepackage[explicit]{titlesec} %
\usepackage{titletoc} %
\usepackage{hhline} %
\usepackage[paperwidth=170mm,paperheight=240mm,textwidth=132mm,top=8mm,bottom=8mm,lmargin=12.5mm,rmargin=12.5mm,
bindingoffset=12.5mm,noheadfoot,nomarginpar,showframe,showcrop]{geometry}
\usepackage[a4,frame,cam,center]{crop} %
\usepackage{hyperref} %
%\titleformat{\part}[display] % for DISPLAY DISPLAY
%{\filcenter \color{black}\itshape\fontsize{15}{18}\selectfont} %
%{\hrule\vspace*{6pt}\\ \color{black}\bfseries\normalfont\fontsize{15}{18}\selectfont{A series of books}} %
%{8pt}
%{\filcenter\partname\hspace{3.2pt}\Roman{part} \hspace{1.8pt}- \hspace{1.0pt}{#1}\\[2pt]\hrule} %
\titlespacing*{\part}{0pt}{132pt}{20pt}[0pt]
\titleformat{\chapter}[display] % for DISPLAY DISPLAY
{\color{blue}\bfseries\itshape\fontsize{12}{15}\selectfont} %
{\color{black}\hspace{30pt}\chaptername\hspace{3.2pt}\normalfont\fontsize{12}{15}\selectfont{\thechapter}} %
{0pt}
{\bfseries\normalfont\fontsize{15}{18}\selectfont{\hspace{21pt}{#1}}} %
\renewcommand{\thepart}{\arabic{part}}
\titlecontents{part}[0em] % for TOC TOC TOC ****************************************************************
{\addvspace{15pt}}
{\textbf{\partname\hspace{4.2pt}\thecontentslabel}} % \partname NOT displayed in contents output on p3 **************
{}
{\titlerule*[18pt]{.}\contentspage\;}
\begin{document}
\pagestyle{empty}
\part{first part}
\tableofcontents
\chapter{The first chapter of part 1} % start of chapter ONE
\part{second part} % start of new part
\chapter{The first chapter of part 2} % start of chapter ONE
\end{document}
