Note: Volumes 1-44 published by Grandi Edizioni Internazionali. Volumes 46-174 were published by Edizioni Periodici Italiani. (#45 was missed in moving from one publisher to another). The known pseudonyms are listed on the third web page above.
Many of these works are listed as translations from works in other languages, but are translated by the same author as wrote the "original" and are listed as such. A few are actual translations of previously existing stories. In many cases, there are additional short stories used to pad out the main (title) story. These short stories were generally written by the same author that wrote the main story, but writing under a different pseudonym.
Although this is a "Horror" series, some books may be non-genre, i.e. may be non-supernatural horror.