\nopagebreak doesn't work between two chapters

Question

All chapters begin a new page by default. I want to remove this break between two short chapters. By the nopagebreak doesn't work. What can be the cause? Is there another way to do that? I don't give all my code there, but I can write some details if needed.

Answer 1

As said, chapter insert a \clearpage, so a simple approach is place the chapter title in a group where this command if redefined to just make a paragraph break, some ornament or whatever that you want. After the group, the old definition of \clearpage is still in effect, so next chapters will start in new pages.

\documentclass{book}
\usepackage{lipsum}
\begin{document}
\chapter{Uno}\lipsum[1]
\chapter{Dos}\lipsum[2]
\begingroup
\def\clearpage{\par}
\chapter{Tres}\lipsum[3]
\endgroup
\chapter{Cuatro}\lipsum[4]
\end{document}