History of Death note

This story neighbor "death note" Light Yagami is the main character, she dreams of youth that seemed destined for success. daily habits bear extraordinary intelligence, starting from a black notebook (death note) strange fall from the sky during the class, not long later he took it. Light Yagami finds the attraction, that Death Note is real, and owned by Ryuk, a Shinigami (Death God).
Each person's name written in the Death Note will die in 40 seconds during the person's name is not the same as some others. But if a unique name, that person will die .... without fail.
With this (death note) bright swear upon the graves that he would 'clean up' world of evil people who inhabit it and not need, thus creating a safe life. From there he thinks he is god