The Tortilla Curtain by T. Coraghessan Boyle

Topanga Canyon is home to two couples on a collision course. Los Angeles liberals Delaney and Kyra Mossbacher lead an ordered sushi-and-recycling existence in a newly gated hilltop community: he a sensitive nature writer, she an obsessive realtor. Mexican illegals Cándido and América Rincón desperately cling to their vision of the American Dream as they fight off starvation in a makeshift camp deep in the ravine. And from the moment a freak accident brings Cándido and Delaney into intimate contact, these four and their opposing worlds gradually intersect in what becomes a tragicomedy of error and misunderstanding.