What a visual masterpiece with a strong story, great actors and lots and lots of layers.
The story
Based on an unfinished story by Edgar Allan Poe this movie takes us along with two lighthouse keepers as they get dropped off at a small remote island with the lighthouse that will be the center of everything they'll do for the coming four weeks.
While they're there, we get to learn more about both of them than we probably would like to - and experience the quiet, the boring, the diffuclt inter-personal, the mythical and the force of nature.
There is also the plot line of someone drifting through life, looking for his own place, who let another man die, assuming his identity. The hallucinations are becoming more and more prominent throughout the story - unclear if that's due to the nature of the existence in someone else's shoes or due to substance abuse or the loneliness of the island life.
All of this in black and white. Beautifully composed, with audio that is sometimes loud or harsh and sometimes eerily quiet and isolating.
The visuals
The film is beautifully shot on Kodak Double X. I sometimes shoot a variation of this film for photography because it's so rich in contrast and sometimes a bit less predictable than others.
This, together with the brilliant set design and lighting choices, the film is not just great to look at, but it takes us into a long bygone era and the tall tales of the seafarers. It also mirrors well how repetitive, lonely and grueling the life on this forsaken place and this line of work are.
The symbolism
The obvious layer is the symbolism of the greek mythology (Thomas Wake invokes Triton, Neptune and is shown like Proteus at times) around the sea and the customs of seafarers (don't kill seagulls, they carry the souls of dead sailors).
A little less obvious is the theme of Howard longing for the light (fire) like Prometheus and overcoming the obstacles, sort of "stealing" the light from Howard - and ending up being punished for it.
You could assign Winslow the role of Sisyphus as well - he tell us all that he ever wanted was his one place. This picture becomes clearer when you consider that all the tedious, hard work he's got to do is ultimately temporary if not futile, plotted against the sheer force of nature they're subjected to. Also, again he is dealing with someone who keeps him from (literally and figuratively) ascending to the light without giving good reasons or a clear path towards his goals.
It visually clearly references a painting by Sascha Schneider ("Hypnosis") in a scene.
Then there's the symbolism of a toxic masculine relationship muddled up with a boy looking for a father figure - the dynamic between the two men is a turbulent one throughout the whole film. Also note both men share the same first name: Thomas. This is about identity in many ways.
Then there's the layer of psychology. Director Eggers explicitely mentions that there's a psychological angle and considering that there's admiration for C.G. Jung, I'd say the themes of guilt and murder (did either of the both men kill another man? Did they just "lose" the men instead?) as well as Jung's concept of the shadow (Wake mentions this at the beginning and we're seeing it throughout: Repressed parts become overpowering for both men) and the oedipal dynamics and power struggles between the men fit in here as well.
The rest
It's just a damn great film with stunning visuals, a well-built atmosphere and lots of angles and layers you can sink into.