Well, without having read it, it's difficult to say precisely. However, generally light novels often center around a particular concept or character. In the case of 'bestia light novel', it could be that the story revolves around a person's encounter with a bestia. This encounter might lead to a series of events that change the protagonist's life, like getting involved in a war between different bestia factions or trying to protect a special bestia from harm.
The book contains stories such as those of heroic quests, magical encounters, and personal growth. They all contribute to the overall charm and depth of 'El Libro de la Vida'.
I'm not sure who exactly Sarah Bello is in the context of scary stories. There could be many people named Sarah Bello, or it might be a relatively unknown figure in a specific collection of scary stories.