[Tex/LaTex] Sub-figures of different sizes grid layout

Question

I have two subfigures that I want to align as such:

But what I got is this with the codes below:

\documentclass{book}
\usepackage{subcaption}
\usepackage{pdfpages}

\begin{document}
\begin{figure}[!htb]
    \centering
    \begin{tabular}[t]{cc}
        \begin{tabular}[t]{c}
            \begin{subfigure}[t]{0.4\textwidth}
                \includegraphics[width=0.9\textwidth]{"fig/example/cat_tall"} 
                \caption{Cat 1} 
            \end{subfigure} 
        \end{tabular}
        &
        \begin{tabular}[t]{c}
            \begin{subfigure}[t]{0.4\textwidth}
                \centering
                \includegraphics[width=0.9\textwidth]{"fig/example/cat1"}
                \caption{Cat 2}
            \end{subfigure} 
            \\
            \begin{subfigure}[t]{0.4\textwidth}
                \centering
                \includegraphics[width=0.9\textwidth]{"fig/example/cat2"}
                \caption{Cat 3} 
            \end{subfigure}
        \end{tabular}
    \end{tabular}
    \caption{Cats}
\end{figure}
\end{document}

Answer 1

You nested tabular ... if you omit the first, the cute cats appear in the image as you desired.

\documentclass{article}
    \usepackage{caption}
    \usepackage{subcaption}
    \usepackage{graphicx}

\usepackage[active,floats,tightpage]{preview}
    \setlength\PreviewBorder{1em}

    \begin{document}
\begin{figure}[!htb]
    \centering
    \begin{tabular}[t]{|c|c|}
    \hline
\begin{subfigure}{0.4\textwidth}
    \centering
    \smallskip
    \includegraphics[width=0.9\linewidth,height=1.7\textwidth]{example-image-a}
    \caption{Cat 1} %{Light Unit}
\end{subfigure}
    &
        \begin{tabular}{c}% if you add [t], than sub images are pushed down
        \smallskip
            \begin{subfigure}[t]{0.4\textwidth}
                \centering
                \includegraphics[width=0.9\textwidth]{example-image-b}
                \caption{Cat 2}
            \end{subfigure}\\
            \begin{subfigure}[t]{0.4\textwidth}
                \centering
                \includegraphics[width=0.9\textwidth]{example-image-c}
                \caption{Cat 3}
            \end{subfigure}
        \end{tabular}\\
\hline
    \end{tabular}
    \caption{Cats}
\end{figure}
    \end{document}

Unfortunately I haven't pictures of cats, so instead of them I use example image from `graphics package and guess about cats heights. Lines in table are added only for orientation to see sub images positions. In final use they should be omitted

Edit: If you add option `[t] to inner table, it will push right sub images down as can be seen on second image (where the height is increased that this can be noticed)