Dear /name/, (sądzę, że wiesz do kogo piszesz)
My name is XYZ and I am a librarian. I AM writing to you because I want to organize a “Youth day of books" for pupils. This event will take place
in the hall of school number 12 in Bydgoszcz on 14th April. I believe that young people will find it intersting.
I do like reading your books, which are griping and electryfing novels. I would like to invite you for the "Youth Day of Books" to Bydgoszcz. I would be honoured if you came. You may read a part of one of your books.
After meeting young people, I would like to organize, with
your agreement, a press conference. It appears tome that the reporters from radio and newspapers will come. I wonder if you like it.
I hope that you kindly accept my invitation.
Your sincerely, XYZ
Styl oficjalnyvvn to nie tylko zwroty typu "your faithfully" (piszemy, gdy nie znamy nazwiska adresata;), czy pełne formy auxiliary verbs. Trzeba też zapanować nad formą budowania zdań, która jest specyficzna, i pamiętać o tym, że w angielskim zawsze trzeba być grzecznym i zostawić odbiorcy pole do własnej oceny. Warto korzystać ze słowników register transfer.