I was reminded of Paterson's utter classic Bridge to Terabithia by Mari Ness's (spoilery) write-up a few weeks ago, and just before my to-read list reached this novel, which also won the Newbery Medal (in 1981, three years after Terabithia.
I didn't quite know what to expect. I was braced for another Terabithia, a closely observed portrait of childhood friendship disrupted by a gut-wrenching plot development near the end. In fact it's very different - Jacob Have I Loved is a story of sibling rivalry, or rather of how the narrator is completely overshadowed by her twin sister. Where the relative normality of the families in Terabithia were a reassuring anchor for the narrative, here the awfulness of Louise's family surroundings, which start bad and keep getting worse, actually makes one almost wish for a Terabithia-style climax. The actual happy ending felt a bit rushed and tacked-on, part of a different story.
But it's still beautifully observed. In the BBC radio series Clare in the Community, there's a hilarious moment in episode 3.2 where Clare's mother is bewildered by Clare's resentment of her sister: "We always were careful to treat them both the same - the plain one and the pretty one!" Jacob Have I Loved isn't a comedy; it's a great portrayal of a despairing teenager, isolated in her own family, which itself is on an isolated island in the Chesapeake Bay, and how she finally gets away.