A knowledge of other texts may inform your reading to a text - How does this relate to 'Frankenstein'?
Not intertextual references made in the novel but relation between themes, characters and narrative structures. How they influence your reading, in particular, your reaction to the characters and their actions.
Any particularly powerful links? Things that really make the reader think and perhaps respond in a different way (ie. a knowledge of Stevenson's 'Jekyll and Hyde' would make a reader of Frankenstein to, perhaps make a psychoanalytic reading and percieve the creature/monster as the dark side of Victor, his personal Hyde)
This is a comparative literature question I believe. Often when we read one novel, its fictional elements are reminiscent of other novels. This means that the plots, characters, theme, symbols and even writing style remind us of other works we have read and can enrich the experience of reading the current work. In the study of literature, we are always comparing and contrasting. English teachers love to assign such writing tasks as "compare the character of Mr. Hyde to Frankenstein's monster," for example. In this way, we as readers can appreciate how different authors treat the same themes or grapple with the same conflicts.
In comparing Dr. Jekyll and Mr. Hyde to Frankenstein, many comparisons can be made because Dr. Jekyll created his own monster, just as Frankenstein did, only Dr. Jekyll's monster was himself, the evil side of himself. Both "monsters" - whether they were separate characters such as Frankenstein's monster or a different side of the same person, as with Mr. Hyde -- symbolized man's inner conflict with good and evil. Wherever you find this conflict in literature, you can make a similar comparison. For example, in the novel Lord of the Flies - you could compare Ralph and Jack. In this novel, Jack is the Mr. Hyde or Frankenstein monster. Or, perhaps you could make a comparison between Frankenstein and Macbeth. Frankenstein's quest to make himself something important in the world of science led to tragedy. Macbeth's quest to make himself king led to tragedy.