Book

% !TEX program = xelatex
% !BIB program = bibtex
\documentclass[a4paper, 12pt, oldfontcommands, final]{memoir}
\settrimmedsize{9.5in}{6.8in}{*}           % 9.5in X 6.8in
\settrims{79.136pt}{53.118pt}              % 
\settypeblocksize{7.8in}{5in}{*}           % 7.8in X 5.2in
\setlrmargins{*}{*}{1}                     % S=0.7in
\setulmargins{*}{*}{.7}                    % U=0.55in+0.3in for header
\trimXmarks
\checkandfixthelayout
\nonstopmode

\usepackage{bookstyle}

% set header
\makepagestyle{mystyle}% name
  \makeevenhead{mystyle}{\thepage}{}{\itshape কম্বিনেটরিকসে হাতেখড়ি}% Even page header
  \makeoddhead{mystyle}{\itshape\rightmark}{}{\thepage}% Odd page header
  \nouppercaseheads
  % Set page style to 'mystyle'
  \pagestyle{mystyle}

\title{কম্বিনেটরিকসে হাতেখড়ি}
\author{আদীব হাসান\\
জয়দীপ সাহা\\
আহমেদ জাওয়াদ চৌধুরী}

\begin{document}
\frontmatter
\include{titlepage}
\tableofcontents*

\mainmatter
% section counter resets with chapter counter
\counterwithin{section}{chapter}
% translate section counter to bangla
\renewcommand\thesection{\thechapter.\tobangla{section}}
% page counter in bangla
\renewcommand{\thepage}{\tobangla{page}}
% Since mainmatter resets \thefigure to \arabic
% translate it back to bangla
\renewcommand{\thefigure}{\thechapter.\tobangla{figure}}

% the chapters that are commented out are not actually in the repo.
% this is just to demonstrate how your project should look like.

% \include{chap/counting_basic}
% \include{chap/probability}
\include{chap/pigeonhole_principle}
% \include{chap/graph_theory}
% \include{chap/induction}
% \include{chap/coloring}

\backmatter
% Since backmatter resets \thefigure to \arabic
\renewcommand{\thefigure}{\tobangla{figure}}
% \include{chap/appendix}
% show all items in bookbib
\nocite{*}
\bibliography{bookbib}
% there are lots of other styles available
\bibliographystyle{abbrv}

\end{document}