There are many ways to tresspass

Tresspass by Valerie Martin is a book that starts slowly and simply but then turns out to have a multi-layered plot.  It's first of all the story of Chloe Dale, a book illustrator, her husband Brendan, a university professor, their only son Toby and his new Croatian girlfriend Salome.  Early in the book Toby and Salome have a lunch meeting with Chloe that does not go well.  Soon Salome is pregnant and the Dale family must adapt to that news. 

There are other stories here as well, primarily of Salome's family but also of the relationship between the young couple, mostly told from Toby's point of view.  After Salome learns that her mother, Jelena, who she believed was dead, is actually alive and living in Italy.  Salome, Toby and Brendan all end up in Italy.  Jelena's account of her experiences during the civil war with the Serbs is interspersed throughout the book and it gives some very graphic details of the war experience.

This is a strong, engrossing, and well written novel that focuses on current social issues (and the war in Iraq is just beginning) as well as marriage and other relationships. My only criticism is that the ending is rather weak.