This show is often compared to The Wire (another fantastic show worth picking up) but other than being cop shows they really have little in common. Whereas The Wire gradually built its story and developed its characters over the course of its five seasons The Shield starts quickly and never lets up.
That's not to say the story is lacking though and, alongside the ongoing story of Vic Mackey, many of the episodes do have individual cases that need solving. Often considered controversial during its lifespan The Shield never holds back on showing and tackling subjects that most shows fear to discuss. It is however the questionable tactics deployed by Vic Mackey and his strike team, a theme that runs throughout the course of the show, that will really have you coming back for more. It is testament to the quality of the writing and acting that most viewers will never make up their minds as to whose side they are really on. I can't recommend this show highly enough.