This is a completely original idea. Its hero or Antihero is an ordinary high school student with an exceptional IQ and skills that allow him to be the first person to hold a book called the "DEATH NOTES".
The rules of the notes are simple.
By writing the target's name inside the book, you have doomed the person.
If no cause has been written, they will die 40 seconds later of a heart attack.
If you specify what they die of, you will get 6 minutes and 40 more seconds to write them down. You can also write when they die, making it faster than 40 seconds or set them to die at a specific time interval.
The last thing is that if you don't know their face or how their name is spelled, then you will not kill the person because the book will not register the person because if you don't know their name, you can't write it in the book and if you don't know the face then you may encounter another person who shares the same name.
[U]
Over the course of the story, additional rules were revealed.
A death god can elongate his life by misregistering other people's names in his book. Say a person was meant to live for 45 years. By putting it down as 25, they add 20 more years to their own life expectancy while shortening that of another.
The death god sent over to "assist" you is technically not on your side, but more like a sideway spectator that only the holder of the Death Note can see and converse. In some cases, the death god can help the Holder of the Death note, but nothing past idle information can be gotten for free.
The holder of the Death note is considered a Death god.
If someone else touches the Death Note, they can see Death Gods.
Anytime you want, you can exchange one of your eyes for a Death god's eye allowing you to see another person's name simply by seeing their face. Your life however, gets halved so if you are expected to live 6 months, it is now 3 monthes.
Death notes usually don't end up in human hands unless the Death god holding one, dies (not likely but it happens), or if another death god can acquire another one from the main death God. If that happens, they can give it to humans or find some other use for it.
Death gods can't see their own life expectancies, even for human Death gods. Death god's can't see another death god's life expectancy either.
Human death gods cannot write their own name inside the death book. They don't die but its not reccommended.
A death god's eraser can cure the problem but the people still retain memory of the the dead universe.
A death God cannot extend another person's life. If they do, they die in the target's place. The dead Shinigami's Death note will be transferred to the person that would have died.
Tearing a few pages out of the book will allow the user to continue using it even without the book.
More rules exist but I'm not sure about them.