It's pretty easy to fancy this film as cool and arty and whatnot, but let's resist the hype and our hunger for coolness for a sec, and see it as it is, shall we?
It is so incredibly empty and banal that it's almost shocking. Simply NOTHING happens in this film in any level. Yes, actors are cool and beautiful, images, too, music, well, I leave that to your taste (I felt like cutting my wrists after a while). But the point is that all these can't do much more than create a feeling, an atmosphere. Could have been a wonderful music video, for example, conveying this particular feeling, but to make it into a 120 mins film without apparent story, message, dynamics, moral/intellectual/character progression, was just a mistake.
SPOILERS.
So, there's Adam, depressed and suicidal throughout the film, no change in mood and facial expression whatever. He composes music but not clear to whom or for what since he truly despises humans and prefers complete anonymity. He doesn't even show his music to his fellow vampire, Eva, because "it's personal". At the same time, it's clearly not enough to cheer him up or give a purpose for his life. His only happy moments are when he takes his actual drug portion (blood in this case, but it's irrelevant). He lives separately from wife whom he adores and longs for, but that doesn't stop him from buying a wooden bullet in order to kill himself.
There's Eve, the wife, whose life is equally without direction or purpose, but at least it doesn't disturb her. She's happy with her books and the company of some fellow superior being and, of course, her actual portion of drug. Her relationship with Adam presented in a totally empty, unsophisticated way, no details, no depth, no answers about how desire could last so long, how their feelings changed during all those centuries. It's empty, colourless, something like a teenage fantasy about "perfect love", which, of course, we all know by age 20, doesn't exists.
And there's Eva, her sister, who is quite irritating and silly, but at least is able to LIVE, inquire, jump in the water and stay open. Of course, she is very quickly kicked out of their life, as she brings danger and questions and unexpected things, and it's just not what those two want. God knows what they want - seemingly nothing.
Quite frankly, it's like an attempt from Jarmusch to pour his pessimism and misanthropy onto the world. Like a massive cry about how lost he feels in this world ruled by senselessness and stupidity and destructiveness. And you could argue that this is the exact purpose of film-making and art in general: paint a picture, hold a mirror to whatever, but to me it's just not good enough to present an "everything is crap" message and leave things to that. It's irritating as a matter of fact. If this is all you can say, go to a therapist and discuss it. If this is what you feel and think that you can offer some kind of solution or answer to it, make a film.