it would be awesome to have, and i've gotten a spell that should theoretically work the same, but i doubt it. first off writting a name down and they die less than a minute later doesn't sound plausable. second, you'd need to concentrait A LOT and put as much energy into it as possible.
if it would work, it's be a curse [or black magic if you want a colour] more important, why would you want it? myself i'd like it because it's a unique book. but to have the power over life and death and have a shinigami with me at all times, meh, doesn't interest me. just enjoy the anime/manga/movies [if you haven't seen them, they're alright. kenichi matsuyama's one of my favourite japanese actors so that made me happy, and i liked the ending more than the manga's... yes i'm also an otaku.]