1. Chapter
1.1 Section
1.1.1 Subsection
1.1.2 Subsection
2. Chapter
2.1 Section
2.1.1 Subsection

1. Chapter
1.1 Section
2. Chapter
2.1 Section

documentclass{book}

setcounter{tocdepth}{1}
begin{document}
tableofcontents
chapter{How to be seen}

section{You see me}

subsection{You won't see me in the Toc}

end{document}