The UK’s Kelly Reilly is among the new arrivals with Rachel McAdams and Taylor Kitsch as production gets underway in California.
The cable network confirmed that Reilly (pictured) has joined the cast to play a former actress and the wife of Vince Vaughn’s mob boss.
HBO previously confirmed Vaughn and Colin Farrell, who plays a corrupt detective in the eight-episode season.
Kitsch, whose last film role was in Lone Survivor and also starred in the US turkeys Battleship and John Carter, will play a police officer with a dark past.
McAdams will portray a straight-laced detective.
HBO is expected to announce the 2015 run date in due course.