One-Way Ticket - William G. Tapply

To help an old friend with a gambling problem, a Boston lawyer confronts the mob in this "fresh and appealing" mystery thriller (Publishers Weekly).
Dalton Lancaster could have been a lawyer, but his heart wasn't in it. He quit Yale after his first year, and used his inheritance to go into the restaurant business, where he might have had some luck if he'd spent more time selling food and less time playing blackjack. As he gambled away his savings, restaurants, and family, his lawyer, Brady Coyne, stuck by him. So when Dalt is beaten up, but not robbed, by three mobsters, Brady can't help but think his friend is gambling again. But Dalton says he has kicked his vice. The attack wasn't a message to him—it was to his son.
Having inherited his father's addiction, Robert is in even deeper trouble than his dad ever was. When he fails to square things with his creditors, he's kidnapped, and Brady is forced to gamble on a long shot: that Robert Lancaster is still alive.