In essence, amid the dark humour and tragedy, I think the film has profound things to say about male pride, and is filled with intriguing ironies (especially concerning Barry Keoghan's character, who is sharper than everyone realises, and who is just as badly treated by Colin Farrell's character as he is treated by Brendan Gleeson's character). On top of that, the story is a fascinating metaphor of the Irish civil war in microcosm. And it's beautifully shot, directed, etc. I said this far more eloquently in my review, hence the link. :)