Meg Schoerke at The Hudson Review:
The Dolphin won the Pulitzer Prize, Lowell’s second, in 1974. It also sparked controversy, due not only to Lowell’s portrayal of Hardwick as the aggrieved, abandoned wife—the “Lizzie character,” as he called her—whom he unflatteringly contrasts throughout to the fecund Caroline character, variously imagined as dolphin, mermaid, and baby killer whale—but also due to his appropriation, and changing, of Hardwick’s letters into sonnets that voice the wife’s side of the story, whether as letter-poems or admonitory echoes that surface in the Lowell character’s head. The awkwardness here of referring to real people as characters reflects the inherent problem with Lowell’s book: the line between fact and fiction is stretched so thin—even to the point of “character” names corresponding to those of their real-life counterparts—that readers are led to assume that the book chronicles reality, not fiction, despite Lowell’s equivocal disclaimer in the final, title poem that the book is “half fiction.”
more here.