Romanticism briefly defined: Romanticism in definitions
Frankenstein is considered the quintessential Gothic novel. To know what that means, read the definition here:
This is quite relevant to Shelley's inspiration! Also, I somehow relate better to this idea better now that we have been through so much isolation: Frankenstein: The Year without Summer
Epistolary novel definition and explanation is here.
Mary Shelley alludes to John Milton's version of the Adam and Eve story (in his epic poem, Paradise Lost). We will not be reading an extra epic poem this year, but it may be helpful to know essentially what Milton wrote.
This link to a teacher explains all of the differences between the 1818 and 1831 editions (with spoilers, obviously). The biggest difference is the backstory of Elizabeth -- step-sister (1831) or cousin (1818).