Whenver you're experiencing a mystery from the point-of-view of the criminal, as you are with Death Note, the real mystery is how to stay ahead of the forces closing in. And this show introduces a worth adversary early on with Detective L, who narrows the source of mysterious deaths to Japan almost immediately, and even suspects the killer doesn't need to be present to commit the murders.
The show also toys with viewers' sense of morality because, yes, using the power of the Death Note, Light Yagami is killing people. But while Dexter had to be taught to channel his psychopathic impulses towards society's worst criminals, Light follows that code naturally.
While the show does ramble at times, and not all phases of the investigation feel as relevant or compelling, overall, the entire experience of Death Note's 37 episodes is a worthwhile rollercoaster.