Comic books about earth bound extraterrestrials tend to fall into one of two categories. There's either the ultra serious book that explores what an alien invasion might be like if it really happened or the cartoony book where the aliens are wiseacres that are way into pop culture and even the villains aren't really all that villainous. Groom Lake splits the difference between the extremes, successfully balancing an incredibly dark set of circumstances and characters with events which have all the levity of a well told "farmer's daughter" joke. It's like the X-Files with a lot more anal probe humor or a version of Men in Black where everyone from the agents to the aliens are a-holes.
The book takes place mostly in New Mexico, where the US government is detaining advanced alien life forms, not ones that have crash landed here, but ones which were invited to the planet so that their technology could be harvested. Of course, not all of the detainees are so willing to be locked up and they often try to escape so that they can either enslave or destroy humanity. Preventing any such disaster, there stands a line of no-nonsense government suits, who will stop at nothing to protect the planet and reverse engineer intergalactic WMDs for Uncle Sam.