Wide Sargasso Sea Jean Rhys' famous prequel to Jane Eyre will completely turn your view of the book and Bertha upside-down.
Wuthering Heights If you're going to read one Brontë sister's work, you might as well read the other. Emily Brontë's Wuthering Heights is striking not only for its story of haunted love, but also for its similarities to Jane Eyre (from the choice for male lead to the mood of the general setting).