It could have been better had it been directed by someone with more experience. Shumlin didn't do a bad job but it is not a great work of cinematic art.
It is, however, a beautiful movie. I have loved it since local channels used to show it. Graham Greene is one of my favorite writers of the last century. Some pretty bad movies were made from his novels and stories. (Many love "The Fallen Idol" but I am not among them. I think I saw "Brighton Rock" once many years ago and liked it but maybe I'm simply thinking fondly of the novel.) This is superbly cast. Charles Boyer does not, it's true, come across as Spanish. But he seems to have the perfect temperament for this character -- tired, wary, caring. Lauren Bacall is appealing as the British girl who falls for him. But the supporting players are the best: Katina Paxinou is excellent. Her performance is a little Grand Guignol, but I attribute that to the director. Peter Lorre, whom we first meet as he gives Boyer a lesson in an Esperanto-like universal language, is excellent -- as always.
And Wanda Hendrix could break the hardest heart. She comes across as a precocious early teenager. The character wants to be helpful. She does her best.
I recommend this movie highly. Not without reservations. The reservation is, primarily, that it is a little stolid. But the story and acting can scarcely be bettered.