\documentclass[twoside,8pt]{extarticle}
\PassOptionsToPackage{
 paperheight =5in, % inherits from class
 paperwidth = 4in, % inherits from class
% inner = , % default 36pt or 0.5in
% outer = , % 36pt or 0.5in
% top = , % 36pt or 0.5in
% bot = , % 36pt or 0.5in
% binding = 9pt, % 9pt or 0.125in
 outerbleed = 9pt, % 0pt, but check with your printer
 innerbleed = 4pt, % 0pt, but check with your printer
% grid  , % 12 it is just a number
% marginalgrid =  , % 3 it is just a number
% marginparsep =  , % 3ex, if using sidenotesplus change to 4 or 5ex
% headsep = , % inherits from class
% headheight = , % inherits from class
% footskip=  , % inherits from class
 show, % a switch to show frames around the printable areas.
% fancyhdrOff
}{flexipage}
\usepackage{flexipage}
\usepackage[]{lucimatx}
\linespread{1.06}
\usepackage{lipsum}
\setlipsum{%
  par-before = \begingroup\color{gray},
  par-after = \endgroup,
  sentence-before = \begingroup\color{gray},
  sentence-after = \endgroup
}

\usepackage{fancyhdr}
\pagestyle{fancy}
\fancyhead[EL,OR]{\thepage}
\fancyhead[ER]{My New Book}
\fancyhead[OL]{Chapter 1}
\renewcommand{\headrulewidth}{0pt}

\usepackage{microtype}

\begin{document}


\begin{verbatim}
\documentclass[twoside,8pt]{extbook}
\PassOptionsToPackage{
  paperheight = 5in, %  inherits from class
  paperwidth =  4in , %  inherits from class
% inner =         , %  default 36pt or 0.5in
  outer =         , %          36pt or 0.5in
% top =           , %          36pt or 0.5in
% bot =           , %          36pt or 0.5in
% binding =       , %           9pt or 0.125in
  outerbleed = 9pt, %           0pt,
  innerbleed = 4pt, %           0pt,
% grid =          , %          12
% marginalgrid =  , %           3
% marginparsep =  , %           3ex,
% headsep =       , % inherits from class
% headheight =    , % inherits from class
% footskip=       , % inherits from class
  show            , % a switch to show frames
% fancyhdrOff       % not using fancyhdr
}{flexipage}
\end{verbatim}
\footnotesize

         \lipsum[10][1-3] \marginpar[{\itshape\tiny\lipsum[1][1-4]}]{\itshape\tiny\lipsum[8]}

         \lipsum[2] \marginpar[{\itshape\tiny\lipsum[1][1-4]}]{\itshape\tiny\lipsum[8][1-5]}

         \lipsum[2][1-6]

~

{\normalsize
\noindent\verb"\NewMarginPage<6ex>{4}" increases marginal and \verb"\parsep" on next page}
\NewMarginPage<6ex>{4} % Increase margin size

         \lipsum[3][1-3]  \marginpar[{\itshape\tiny\lipsum[1][1-4]}]{\itshape\tiny\lipsum[10][1-4]}

         \lipsum[1][1-8]

       \lipsum[2][1-7]

~

{\normalsize
\noindent\verb"\ResetFlexiPage" to original page setup with the narrower margin}
\ResetFlexiPage

         \lipsum[10][1-5] \marginpar[{\itshape\tiny\lipsum[1][1-4]}]{\itshape\tiny\lipsum[1][1-3]} \lipsum[2]

~

{\normalsize
\noindent\verb"\Lanscape" enters landscape mode}
\begin{Landscape} % enter lanscape mode,

         \lipsum[1-4]

~

{\normalsize
\noindent\verb"\endLandscape" exits landscape mode }
\end{Landscape} % exit lanscape mode,
         \lipsum[2][1-5] \marginpar[{\itshape\tiny\lipsum[1][1-4]}]{\itshape\tiny\lipsum[1][1-3]} \lipsum[11]

~

{\normalsize
\noindent\verb"\begin{landscape}" enters landscape environment}
 \begin{landscape}
 \lipsum[2-5]
 \end{landscape}
{\normalsize
\noindent\verb"\end{landscape}" exits landscape environment}

~

 \marginpar[{\itshape\tiny\lipsum[1][1-4]}]{\itshape\tiny\lipsum[1][1-3]}  \lipsum[17]

~

{\normalsize
\noindent\verb"\NewFullPage" enters full page mode}
\NewFullPage

         \lipsum[1-4]

~

{\normalsize
\noindent\verb"\OldMarginPage " restores the previous page format}
\OldMarginPage

 \marginpar[{\itshape\tiny\lipsum[1][1-4]}]{\itshape\tiny\lipsum[1][1-3]}  \lipsum[17]



\end{document}