\documentclass[12pt,english]{reading-letter}
\usepackage[utf8]{inputenc}

\graphicspath{{../assets/}{./fig/}}
\DeclareGraphicsExtensions{.png,.pdf,.jpg,.jpeg}

% to add a box around the address => useful when using a letter with a window
\fenstermarken

\Name                {Dr. Julian M. Kunkel}
\Building           {Polly Vacher}
\Street             {}
\POBox              {}
\Qualification      {}
\JobTitle           {Lecturer}
\Unit               {Computer Science Department}
\HTTP               {https://hps.vi4io.org}
\HTTPUnit           {http://www.reading.ac.uk/computer-science}
\Campus             {Whiteknights}
\City               {Reading RG6 6AY}
\Phone              {+44 118 378 8218}
\Country            {UK}
\EMail              {j.m.kunkel@reading.ac.uk}
%\Reference          {Ref:}


\renewcommand{\blztext}{\footnotesize BIC}
\renewcommand{\kontotext}{\footnotesize IBAN}


%If you want to embed a signature into the PDF:
%\Signature        {\includegraphics{unterschrift.png}\\ Dr. Julian M. Kunkel}
\Signature        {Dr. Julian M. Kunkel}

\Adress             {Bla\\Where\\x}

\Subject            {Letter of recommendation}
\Date               {\today}
\Opening            {Dear Madam and Sir,}
\Greeting           {Cordially}{1cm}

\begin{document}
\begin{readingLetter}
% for longer letters:
% \setlength{\parindent}{15pt}

This is a trivial letter.

\end{readingLetter}
\end{document}