\documentclass[a4paper]{boek3}
\usepackage[english,finnish]{babel}
\usepackage{noto-serif}
\usepackage{cmap}
\usepackage{subfiles}
%\usepackage{censor}

%\StopCensoring

\title{Kirja}
\author{Kirjailija}
\date{\today}

% Removes empty ToC page
\let\cleardoublepage=\clearpage

\begin{document}
\maketitle
\tableofcontents
\subfile{luvut/1}

\end{document}