Flight Behavior by Barbara Kingsolver. Hardcover.
Dellarobia Turnbow got pregnant in high school; now, some 11 years into her unhappy marriage, she's ready for a big change, and she things she's found it with a randy young telephone lineman. But on her way to a rendezvous, she is waylaid by the sight of a forest ablaze with millions of butterflies. Their usual migratory route has been disrupted, and what looks to be a stunningly beautiful view is really an ominous sign. for the Appalachian winter could prove to be the demise of the species. The phenomenon draws the whole world to Dellarobia's doorsteps -- scientists, the media, hordes of tourists -- and gives her new and galvanizing insight into her poverty-stricken life on the sheep farm of her disapproving in-laws.