The film creates a melancholic feeling of nostalgia. Viewers, who are able and willing to engage with it, will "mourn"/suffer with the characters and for the characters who, with all their hopes, dreams and (hinted) regrets, remain victims of their time or prisoners of their unlived lives.
Yvonne's sensualité, which is not an eroticism à la américaine, is, above all, part of her wider appeal: With Yvonne there is light, hope (America), dreams and the possibility of an escape from the existence of everyday life for Victor and Dr. Rene.
However, both characters seems to sense that these dreams and hopes are as éphémères as the summer they spend with Yvonne.
The melancholy in this film may be a bit on the sentimental side, which happens when you link it to nostalgia (but not necessarily as "In the Mood for Love" shows).
But I'd recommend it anytime, esp. If you have a chance to watch it in a cinema.
