The title The First Stone is an allusion to a famous moment in Jesus's ministry when a married woman was caught having an affair, and the community lines up to stone the woman to death. Jesus writes something in the sand (no one knows what exactly) and then said, "Whoever has never sinned; you cast the first stone." He saves the woman's life by proving that no one should judge her, because people aren't always the wisest judges.
That is the exact place we find our protagonist, trapped in his anger, stone in hand, ready to punish the universe for not giving him what he wants. When he decides to throw the stone anyway, against moral advise, he initiates his fate.
Reef's fate is that he will have to come to terms with the true gravity of the situation. Toward the end of the novel, Leeza Hemming and Reef figure out that Reef was responsible for causing the car accident that almost killed her and put her in rehab.
Leeza and Reef don't become fast buddies after that, and the affirmation, intimacy, and approval that Reef so desperately craves throughout the book—those things are denied to him, because he allowed his egotistical emotions to provoke him to literal violence. This constitutes a tragic fall, and the hero in question realizes too late that he has already stolen the thing he wants most from himself by his pride.
