Time warp stories are not easy to make, and they tend to be unoriginal. However, this one is not only well done but also fresh and unusual. The hero and heroine are separated in time, but only by two years. They live in the same beautiful house at a lake; Kate (Sandra Bullock) in 2006, and Alex (Keanu Reeves) in 2004. The twist takes some time to figure out, both for the characters and for the first-time viewers. Kate and Alex communicate through letters that they put in the mailbox at the house; somehow, the mailbox serves as a portal and delivers their letters to each other, through time. I have seen the idea criticised in some reviews; yes, in order to enjoy this film you have to stop wondering how it works and just accept it.
Sandra Bullock is, as always, excellent. Keanu Reeves is rather reserved in this film, which I guess fits the role of a lonely, introverted architect. The two do not have much screen time together as their romance develops through correspondence, but you can still feel the chemistry between them. I would describe this movie as exceptionally good.