The editions of 1818 and 1831 are different in quite a few aspects, one of which is the number of chapters. The new version contains a different story of Elizabeth and several changes in the story structure.
Detailed answer:
Mary Shelley’s novel, Frankenstein; or, The Modern Prometheus has two main editions: 1818 and 1831. They are slightly different due to the criticism of Shelley’s writing. The earlier one was the original publication. In the second version, Shelley changed the story structure and character portraits. Now the 1831 edition is considered the main one.
The most apparent change is the development of the first chapter. The introduction is made larger and split in two, making the book 24 chapters long. Another change is the correction of Elizabeth’s origins. In the original, Victor Frankenstein’s beloved one was his cousin. It caused debates in literary circles. In the next release, Elizabeth became an adopted sister.
Shelley tried to answer the criticism. She provided more character motivations and explained Victor’s actions. As a result of all the changes, the tone and themes of the story shifted. Initially, Victor represented vanity in the face of natural laws. He was an ambitious scientist suffering from his research. In the next edition, as noted by Edward James, Frankenstein becomes a tragic hero. Now he is a victim of destiny who faced the death of his loved ones.