Actually stunning. 1917 is the type of epic film that will take you by the shoulders and tell you a story, regardless of your feelings.
The story line is simple and totally wild all at once and the brilliant one-shot style visuals make it feel more like a memory than a movie. The entire film thoroughly drills into you how hellish WWI was on what can be assumed would be its best days. Then, once it's succeeded in making the characters feel as real as the person sitting next to you, it really hits you with how horrendously it must have affected the people who lived through something similar during the war.
It is completely appalling in the best possible way and absolutely will not let you try and sugar-coat its history. You just might only be able to describe it as hauntingly, tragically beautiful.
It's not a documentary or a reference film, nor is its job to be the most accurate war movie ever. It's meant be bring history to life and not let you forget it.