Why is Frankenstein a classic?
It was the first novel of its kind to address a theme that has become quite common across science fiction–the notion of technology progressing to the point of going beyond God’s will, and humans suffering because of it. A huge part of this novel is the creation of artificial life that is so intelligent, it realizes it’s not human. It understands the beauty of human experience and is pissed that it can’t experience it for itself. Therefore, it rebels against its creator. This is the same theme of 2001, A Space Odyssey, Blade Runner (“Do Androids Dream of Electric Sheep?”), and many other famous works of science fiction. Shelley was the first, so it’s considered the classic.