I love this franchise, I watched the original series as research for my final project in College and I loved the films that followed. Death Note's about a notebook that kills anyone who's name is written in it and this chap called Light finds it and he uses it to kill criminals, this catches the attention of the police and they bring in this secretive but incredibly talented Detective who goes by the name 'L' to find out who's behind the killings. Here's a trailer for the films.
Here's the Dubbed trailer for people who don't like subtitles
Oh, Shinigami = A Grim Reaper of sorts
and here's a (superior) subbed trailer for people who don't like dubbed films.
The trailers don't really do it justice but the Death Note films are well worth checking out if you get the chance.