The Rest is Silence by Carla Guelfenbein
As the adults sit down to gossip over a long wedding lunch and the rest of the children rush off to play, a young boy slips out of sight beneath the table. Tommy is twelve years old but his weak heart prevents him from joining his cousins' games, so he sets his MP3 player to record the voices chattering above him. But then the conversation turns to his mother's death and he overhears something he was never meant to know: that she didn't die of an illness, but took her own life. Confused and hurt, Tommy keeps what he has learned to himself and begins his own secret investigation into what really happened. At the same time, his father and stepmother have problems of their own to contend with. Juan is racked by private grief and guilt after the death of one of his patients, and Alma, his second wife, senses an increasing distance in their marriage and gradually finds herself drawn back towards an old flame. As all three withdraw into their own worlds, leaving more and more unsaid between them, their family story moves inexorably, affectingly towards its devastating conclusion.