Walpole uses an unusual format for the frame story in The Castle of Otranto, constructing it in a way that makes its origins seem shrouded in myth—much like the medieval tales it echoes. Although he wrote the book himself, Walpole claims (in the First Edition Preface) that it was:
found in the library of an ancient Catholic family of the North of England. It was printed at Naples, in the black letter in the year 1529 [...] If the story was written near the time it was supposed to have happened, it must have been between 1095, the era of the first crusade, and 1243, the date of the last, or not long afterwards.
These claims to an ancient origin seem almost laughably false, and are certainly tongue-in-cheek. However, the author's inclusion of them suggests that the story should be interpreted along these lines by the reader. The "black letter" that Walpole mentions here refers to Gothic script, a medieval form of writing that fell out of use in the early 17th century. Walpole's choice to describe a detail as tiny as the type of script used deepens the imaginary mythology around this "ancient" book he "found." Small details like this make the frame story of The Castle of Otranto feel realistic; the reader can almost see the dense, spiky Gothic writing in front of their eyes.
He also claims, in this Preface, to have only translated the novel, using this as an opportunity to clearly state the moral alignment of the story:
It is natural for a translator to be prejudiced in favour of his adopted work. More impartial readers may not be so much struck with the beauties of this piece as I was. Yet I am not blind to my author’s defects. I could wish he had grounded his plan on a more useful moral than this: that “the sins of fathers are visited on their children to the third and fourth generation.”
The cheeky tone in which Walpole criticizes his "author's defects" is amusing for the reader. What's more, it also allows Walpole to explain that he wants readers to understand the "sins of fathers" and how the immoral behavior of one generation passes to the next. Later, in the Second Preface, Walpole explains his choice to do this, and also gives the reader more suggestions for how to interpret the book. He notes that the "seriousness" of the domestic servants and the intensity of the book's characterization— among other things—were an attempt to "blend" the genres of literature he was working on. In the First and Second Edition Prefaces, Walpole provides both a fantastical "origin" (that is, the framing for the novel) and instructions to his readers on how it should be read.
