Two responses, here.
Since nextpage.sty is already loaded, one could just use that multi-feature package. In the following, the original “add this line” line is commented and the nextpage.sty \cleartooddpage command is added, as indicated.
\documentclass[a5paper,10pt, twoside]{book}
\usepackage{fancyhdr}
\pagestyle{fancy}
\fancyhead{} % clear all header fields
\fancyfoot{} % clear all footer fields
\fancyhead[RO]{The College Savings Factor} %title of the book
\fancyhead[LE]{\chaptername \ \thechapter}
%\fancyfoot{} % clear all footer fields
%\fancyfoot[LC,RC]{\thepage}
\renewcommand{\headrulewidth}{0.2pt}
\renewcommand{\footrulewidth}{0.0pt} % 0.0 makes line dissapear
\fancyfoot[LE, RO]{\thepage}
\usepackage{nextpage}
%%%\usepackage{emptypage} %%<--- add this line
\begin{document}
Chapter 1
text
%%%\cleardoublepage
\cleartooddpage[\thispagestyle{empty}] %%% <-- this line added
Chapter 2
text
\end{document}
Since what’s addressed in both the MWE and the original (2015) Answer are simulated chapters, and since actual chapters have unique features to handle sometimes, an example of actual chapters using nextpage.sty with the book class is also included. Some designs call for “no formatting,” as is the case with the OP. Some designs call for “page number only;” some, “This page intentionally blank,” with or without page numbering. nextpage handles all of these options, as illustrated in the following. Various options are retained as comments that illustrate further customization options.
\documentclass[a5paper,10pt, twoside]{book}
\usepackage{tocloft}
%https://tex.stackexchange.com/questions/142871/how-to-customize-a-brief-table-of-contents-generated-from-tocloft-and-shorttoc-i
%https://tex.stackexchange.com/a/250822/170846
\setlength\cftbeforetoctitleskip{0pt} % change space before TOC title
\setlength\cftaftertoctitleskip{20pt} % change space after TOC title
\usepackage[latin,english]{babel}
\usepackage{csquotes} % smart quotes
\usepackage{fancyhdr}
\pagestyle{fancy}
\renewcommand{\chaptermark}[1]{\markboth{#1}{#1}}
\newcommand{\resetHRule}[1]{\renewcommand\headrulewidth{#1}}
\newcommand{\setHdrFtr}[0]{%
\fancyhf{}%
\fancyhead[RO]{The College Savings Factor}%
\fancyhead[LE]{\leftmark}%
\renewcommand\footrulewidth{0.2pt}
\fancyfoot[LE, RO]{\thepage}%
}
\fancypagestyle{plain}{%
\fancyhf{}
\renewcommand\headrulewidth{0pt}
\fancyfoot[LE, RO]{\thepage}
\renewcommand\footrulewidth{0pt}
}
\newcommand{\clrHdr}[0]{
\thispagestyle{plain}
}
\usepackage{nextpage}
%%% minor modification to nextpage for even-to-even clearing
\makeatletter
\renewcommand{\cleartoevenpage}[2]{%
\ifodd\c@page\clearpage%
\else\newpage\thispagestyle{#2}\hbox{}#1
\newpage\hbox{}
\fi}
\makeatother
\usepackage[texcoord]{eso-pic}
\usepackage{graphicx}
\usepackage{url}
\usepackage{lipsum}
\usepackage[pagebackref=true]{hyperref}
\hypersetup{
colorlinks=true,
linkcolor=blue,
filecolor=blue,
urlcolor=blue,
}
\setcounter{tocdepth}{1} % -1, 0, 1
\begin{document}
\clrHdr
\renewcommand{\contentsname}{Contents}
\phantomsection
\addcontentsline{toc}{chapter}{Contents}
\tableofcontents
% odd to odd -- blank
\cleartooddpage[\thispagestyle{empty}]% <--- square
% odd to odd -- blank (w/ pg no.)
%\cleartooddpage[\thispagestyle{plain}]
\phantomsection
\addcontentsline{toc}{chapter}{Chapter 1}
\chapter*{Chapter 1}
\chaptermark{Chapter 1}
\setHdrFtr
\lipsum[44-48]
% odd to odd -- skipped pg filled (no page number)
\cleartooddpage[{\vspace*{\fill}\begin{center}THIS PAGE LEFT BLANK\end{center}\vspace*{\fill}}\thispagestyle{empty}]
% odd to odd -- skipped pg filled (with page number)
%\cleartooddpage[{\vspace*{\fill}\begin{center}THIS PAGE LEFT BLANK\end{center}\vspace*{\fill}}\thispagestyle{plain}]
% odd to odd -- just page number
%\cleartooddpage[\thispagestyle{plain}]
\phantomsection
\addcontentsline{toc}{chapter}{Chapter 2}
\chapter*{Chapter 2}
\chaptermark{Chapter 2}
\lipsum[49-51]
% even to odd -- blank and
% even to odd -- filled
% are the same -- there is no blank page to handle
\cleartooddpage[{\vspace*{\fill}\begin{center}THIS PAGE LEFT BLANK\end{center}\vspace*{\fill}}\thispagestyle{plain}]
\phantomsection
\addcontentsline{toc}{chapter}{Chapter 3}
\chapter*{Chapter 3}
\chaptermark{Chapter 3}
\lipsum[52]
% odd to even -- blank and
% odd to even -- filled
% are the same -- there is no blank page to handle
\cleartoevenpage{some text that won't ever show up}{plain}
\phantomsection
\addcontentsline{toc}{chapter}{A plain PreChap page}
% for no page number
%\thispagestyle{empty}
% for page number
\thispagestyle{plain}
This is the recto page that was advanced/cleared to. Typically, there'll be pre-chapter text or graphics on this page.
\clearpage
\phantomsection
\addcontentsline{toc}{chapter}{Chapter 4}
\chapter*{Chapter 4}
\chaptermark{Chapter 4}
\lipsum[53-56]
% even to even -- blank (w/ pg no)
\cleartoevenpage{}{plain}
% even to even -- blank (w/o pg no)
%\cleartoevenpage{}{empty}
\phantomsection
\addcontentsline{toc}{chapter}{PreChap Graphics with preceding blank page with page no}
\thispagestyle{plain}
%adapted from https://tex.stackexchange.com/a/248829/170846
\begin{minipage}[c]{\textwidth}
\href{https://ctan.org/lion/files/ctan_lion_350x350.png}{\includegraphics[scale=0.75]{ctan_lion_350x350.png}{}}\\
\end{minipage}
\clearpage
\phantomsection
\addcontentsline{toc}{chapter}{Chapter 5}
\chapter*{Chapter 5}
\chaptermark{Chapter 5}
\lipsum[57-60]
% even to even -- skipped pg filled (w/ page no)
\cleartoevenpage{\vspace*{\fill}\begin{center}THIS PAGE LEFT BLANK\end{center}\vspace*{\fill}}{plain}
% even to even -- skipped pg filled (no page number)
%\cleartoevenpage{\vspace*{\fill}\begin{center}THIS PAGE LEFT BLANK\end{center}\vspace*{\fill}}{empty}
% even to even -- skipped pg w/ page number only
%\cleartoevenpage{}{plain}
\phantomsection
\addcontentsline{toc}{chapter}{The \enquote{cleared-to} verso page, ready for pre-Chap content, with preceding Notice of deliberate blankness}
\thispagestyle{plain}
% or, for no page no.
%\thispagestyle{empty}
Here is a famous quote by a famous author.
{\textit{Famous Author}}
\clearpage
\phantomsection
\addcontentsline{toc}{chapter}{Chapter 6}
\chapter*{Chapter 6}
\chaptermark{Chapter 6}
\lipsum[70-73]
\end{document}
\chapter{Chapter 2} text`?
– moewe Sep 16 '15 at 15:23