Letters to Milena, a book in which Franz Kafka collected some of his letters to Milena Jesinska, a Czech journalist, from 1920 to 1923.
The ability to write letters so easily must have brought ruin and destruction to the souls of this world. Writing letters is in fact intercourse with spirits, and this does not mean only the soul of the addressee, but also the people who have a soul, and this develops secretly in the letter that one writes.