Girls starts with a bizarre, but interesting premise -- a weird tribe of beautiful (nude) (probably alien) clone-"girls" takes over a small town, killing the human women and seducing the human men in order to get impregnated and make more clone-"girls". The girls' behavior has additional layers of weird alien purpose, but the interesting stuff is baked into how the town reacts to this basic concept -- the ways that the men and women turn on one another in order to deal with the invasion.
Both the script and the visuals are, generally, pretty weak -- it's paced like a horror movie, which is nice, but on a panel-for-panel basis the drawings are flat and totally over-photoshopped, and the dialogue is incredibly wooden. It's difficult to tell when the Luna brothers are trying to create one-dimensional caricatures of loathsome people in order to demonstrate who the villains are, and when they're inarticulately attempting to express their own ideas about gender dynamics. In interviews from the time when the comic series was originally being published, the brothers argued that they were attempting to represent both genders equally, and I'm relatively sure that this is true. But at the end of the day this is still a book created by two dudes in their mid-twenties, and it shows.
To wit: the protagonist is a young guy who's the town outcast because he just got dumped and no one understands how horny he is. While other characters flutter in and out of having brief periods of narrative agency, he's the only one who keeps his head on straight throughout the story. The other characters, men and women alike, usually meet their demise because they are A) too horny or B) not horny enough. I guess you could say there's something sort of interesting here about the value of being at peace with one's own sex drive, but that's a pretty big stretch. Mostly, the horny/not-horny binary ensures that the rest of the cast is either depicted as a bunch of lecherous fuck-trolls, or frigid (or gay, which seems to be a third category because blech).
I think the most compelling thing about the book is waiting for the other thematic shoe to drop -- like when you read an undergraduate short story about race just waiting to see when the student uses the 'n' word. For all the Luna Bros. talk on gender equality, the whole "monsters only kill women" concept is basically a convenient way for a bunch of lame-ass dudes to learn how to be "real men" by saving the ladies over and over from beginning to end, while the one woman who does some saving herself is depicted as a horrible psychotic shrew. That SOME of the men are revealed as scumbags doesn't really balance out the basic fact that ALL the women have to learn to let themselves be taken care of in order to survive.
Plus this is a 700-page book that is essentially an excuse to write and draw a lot of fucking, and we never see a single dick.
None of this is to say that 25 year olds are incapable of telling good stories -- just that these 25 year olds weren't capable of telling this one.