Wide Sargasso Sea is a response to Charlotte Bronte's Jane Eyre. It is important because it presents a completely different perspective of the character of Edward Rochester's first wife. It also explores issues of postcolonialism and specifically the relationship between the West Indians and the English in the post-emancipation Caribbean, exposing the attitudes which allow the domination of one race over another.
In Jane Eyre, Rochester's wife Bertha is depicted solely as a madwoman, subhuman, a dangerous and promiscuous monster locked away in the attic, and Rochester as the innocent and unhappy victim of an arranged marriage. In Wide Sargasso Sea, Bertha is called Antoinette, a real person with needs and motivations for the things she does. A child of mixed race, Antoinette has been an outcast all her life. Although her marriage with Rochester is indeed arranged by others, it is his rejection and revulsion to her sensuality and mixed heritage which drives her to the brink of insanity.