The cinematography looks great and the movie, interesting. I don't think any movie can accurately capture the horrors that Dunkirk was and I don't think I would want to see a movie that did.
It is an important piece of history though.
Quote: The Dunkirk evacuation, code-named Operation Dynamo, also known as the Miracle of Dunkirk, was the evacuation of Allied soldiers from the beaches and harbour of Dunkirk, France, between 26 May and 4 June 1940, during World War II. The operation was decided upon when large numbers of Belgian, British, and French troops were cut off and surrounded by the German army during the Battle of France.
In a speech to the House of Commons,
British Prime Minister Winston Churchill called the events in France "a colossal military disaster", saying "the whole root and core and brain of the British Army" had been stranded at Dunkirk and seemed about to perish or be captured. In his We shall fight on the beaches speech on 4 June, he hailed their rescue as a "miracle of deliverance
https://en.wikipedia.org/wiki/Dunkirk_evacuation