Memento has one of the most unique narratives ever created. It starts with a photo developing backwards and then tells its story in reverse chronology. The color sequences play backwards and black and white scenes play forward. This is to create a feeling similar to that of the main character, we and Leonard can't remember what took place before the present. This also allows for the surprise revelation at the end.
There are a few of us that wished Nolan hadn't wasted his time on the Batman crap. 'Following' was quite good, and this one made use of a great group of actors at the top of their game. I think you have to give it to Pantoliano for being the glue that kept the whole thing working. For some reason it doesn't seem to reward multiple viewings.