Tukukkk

I want center the title "Preface" and "Abstract" only. I do not want to centralize all the chapters. I can not and I should not delete any bookstore, I need all the libraries.

documentclass{book}

usepackage[left=3cm, right=2cm, top=2cm, bottom=2cm]{geometry}

usepackage{lipsum}

usepackage{lscape}

usepackage[utf8]{inputenc}



usepackage[spanish,es-tabla]{babel}



usepackage[table]{xcolor} 



usepackage{sectsty}

sectionfont{fontsize{12pt}{14.4pt}selectfontsffamilybfseries}

subsectionfont{fontsize{11.5pt}{13.8pt}selectfontsffamilybfseries}

subsubsectionfont{normalsizesffamilybfseries}







begin{document}



chapter*{centering Preface}





Some text

chapter*{centering Abstract}





chapter{Introduction}

chapter{Body}

chapter{Conclusion}



end{document}

Set the title inside a makebox[linewidth]; this naturally centres it. It would not have any impact on headers or the ToC since these elements don't end up there.

documentclass{book}



usepackage{lipsum}



begin{document}



chapter*{makebox[linewidth]{Preface}}

lipsum[1]



chapter*{makebox[linewidth]{Abstract}}

lipsum[2]



chapter{Introduction}

chapter{Body}

chapter{Conclusion}



end{document}

Using the tools from sectsty:

documentclass{book}

usepackage[left=3cm, right=2cm, vmargin=2cm]{geometry}

usepackage{lipsum}

usepackage{lscape}

usepackage[utf8]{inputenc}



usepackage[spanish,es-tabla]{babel}



usepackage[table]{xcolor}



usepackage{sectsty}

sectionfont{fontsize{12pt}{14.4pt}selectfontsffamilybfseries}

subsectionfont{fontsize{11.5pt}{13.8pt}selectfontsffamilybfseries}

subsubsectionfont{normalsizesffamilybfseries}



begin{document}



chapterfont{hugebfseriescentering}

chapter*{centering Preface}



Some text

chapter*{centering Abstract}



chapterfont{hugebfseriesraggedright}

chapter{Introduction}

chapter{Body}

chapter{Conclusion}



end{document} 

Fast solution

You could set a manual space

chapter*{hspace{.4textwidth}Preface}

which puts the title almost in the middle of the page

Reasoned solution

Otherwise you could think of measuring the length of your title and make the thing more precise with the package calc

%PREAMBLE

usepackage{calc}



newlengthmylen

newcommandchaplen[1]{

    setlengthmylen{(textwidth-widthof{Hugebfseries #1})/2}

}



%... BEGIN DOCUMENT



chaplen{Preface}

chapter*{hspace*{mylen}Preface}



chaplen{OTHER}

chapter*{hspace*{mylen}OTHER}

FUll code:

documentclass{book}

usepackage[left=3cm, right=2cm, top=2cm, bottom=2cm]{geometry}

usepackage{lipsum}

usepackage{lscape}

usepackage[utf8]{inputenc}



usepackage[spanish,es-tabla]{babel}



usepackage[table]{xcolor} 



usepackage{sectsty}

sectionfont{fontsize{12pt}{14.4pt}selectfontsffamilybfseries}

subsectionfont{fontsize{11.5pt}{13.8pt}selectfontsffamilybfseries}

subsubsectionfont{normalsizesffamilybfseries}



usepackage{calc}



newlengthmylen

newcommandchaplen[1]{

    setlengthmylen{(textwidth-widthof{Hugebfseries #1})/2}

    }



begin{document}



chaplen{Preface}

chapter*{hspace*{mylen}Preface}





Some text

chaplen{Abstract}

chapter*{hspace*{mylen}Abstract}





chapter{Introduction}

chapter{Body}

chapter{Conclusion}



end{document}