A writer of witty comedies of manners, Schine (Rameau's Niece; The Love Letter) combines the intellectual curiosity of a philosopher with a lively sense of the absurd. Her latest comically misadventurous, existential inquiry is set in the Galapagos, and Darwin's Origin of Species serves as a framework for protagonist Jane Barlow Schwartz's search for identity. Newly divorced Jane arrives at the islands off Ecuador to find that the park ranger who will guide her group is her estranged cousin, Martha Barlow, her dearest friend when they were growing up in Barlow, Conn., the town named for their family's founders. Jane has been grieving for years because Martha suddenly ended their ""twinship"" without explanation. Suspecting that Martha's rejection may be tied to the mysterious family feud that the elder Barlows will not explain, Jane speculates about the ways Darwinian theory can be applied to human relationships. For Jane, the question of ""the transmutation of friendship"" takes on the urgency of a scientific quest, which she pursues in whimsical fashion, inadvertently getting herself into hilarious situations--especially when she thinks she is competing with Martha for the attentions of an attractive young man in her group, one of many vividly realized characters who, to Jane's eye, are colorful examples of species diversity. But Martha's essential difference from Jane, her confident, pragmatic and unimaginative personality, becomes clear to the reader before Jane gets a clue. Cleverly, Schine follows Jane's epiphany about friendship and self-knowledge with a truly surprising revelation about the Barlow family feud. The sophisticated narrative, sparkling with playful intelligence and resonating with poignant insights about the ways girls and women bond, is Schine's best novel yet. Agent, Neil Olson of Donadio & Ashworth. 75,000 first printing; author tour. (Oct.) FYI: A movie titled The Misadventures of Margaret, based on Rameau's Niece, will be released in the fall. The Love Letter is in production from DreamWorks.