Jacob Have I Loved revolves around the sibling rivalry between Louise and Caroline Bradshaw. The combination of envy, love, and hatred that twists Louise's relationship with Caroline realistically reflects the insecurity and competitiveness experienced by most children. Even children without siblings are often subjected to negative, haunting comparisons with relatives and peers. Louise's jealousy of the beautiful, talented Caroline threatens to embitter her for life; her ultimate victory offers encouragement to readers coping with similar situations.

Paterson also creates a fascinating portrait of life on Rass Island, a fictional spot patterned after real towns along the Chesapeake Bay. Life on the island revolves around fundamentalist religion, seasonal fishing for crabs and oysters, and the often fulfilling lives of those who "follow the water." The men lead rugged, dangerous lives, but Paterson chooses to focus on the women of the island. Because the women are expected and encouraged to stay home, the scenic island seems for them less a place of pleasure than a place of entrapment. Paterson's exploration of the psychological effects of this lifestyle lends depth and authenticity to the work.