You can go with fncychap if you want. It uses commands (like \rm) which are deprecated for right about 20 years now. To be honest, i think it is pretty ugly. Other people are making fun of it as well (but in conjunction with Comic Sans).
I changed your code a bit, please have a close look.
Code: Select all
% arara: lualatexmk\documentclass[10pt,english,british,twoside,openany]{scrbook}\usepackage{blindtext}\usepackage[automark,headsepline,footsepline=.25pt]{scrlayer-scrpage}\pagestyle{scrheadings}\addtokomafont{pageheadfoot}{\slshape}\addtokomafont{pagehead}{\tiny}\addtokomafont{pagefoot}{\small}\addtokomafont{disposition}{\rmfamily}%JB: rm for chapter headings%\ohead{\MakeUppercase{\leftmark}}%JB: do you REALLY want this%uppercased?\ohead{\leftmark}\ihead{Ben Francis}\ofoot{\mytitle}\cfoot{\pagemark}\usepackage{microtype}\usepackage{ragged2e}%\usepackage[Lenny]{fncychap}%really ugly\usepackage{graphicx}\usepackage[british]{babel}\renewcommand\thepart{\Alph{part}}%\newcommand{\apostrophe}{\XeTeXglyph\XeTeXcharglyph"0027\relax}%JB: Since you are using XeTeX, take advantage of fontspec%JB: LuaTeX and microtype work better together, so LuaLaTeX\usepackage{fontspec}\setmainfont{Linux Libertine O}%JB: Just as an example%\KOMAoptions{open=any}%\setlength{\headheight}{15.2pt}%\widowpenalty=300%\clubpenalty=300\renewcommand*{\partpagestyle}{empty}\usepackage{geometry}\geometry{paperwidth=5.06in,paperheight=7.81in,verbose,tmargin=0.5in,bmargin=1in,inner=0.75in,