Okay, so it's not really about boredom. Though, if you're trying extremely hard, you can wring out the moral that "idle hands are the devil's tools" or something like that. In this case, it's true.
Light Yagami is bored. He just so happens to be highly intelligent student in Japan, as well. (He also has somewhat evil tendencies. Go figure.) He's good at pretty much everything he does. He's even pretty popular at school. His dad's a police officer, so Light realized early on that the justice system was corrupt. He wanted to do something to change it, but what? Maybe he wouldn't have done anything at all, had Ryuk been happy.
Unfortunately for him, Ryuk was bored too. And Ryuk was a Shinigami. (Shinigami=death god.)
Shinigamis were the ones who choose how someone will die, at least in Light's world. They used death notes to write down how, when, and where someone would die. They weren't supposed to give them to humans.
But Ryuk was oh so very bored. He dropped his death note, and Light found it.
Unlike most intelligent people who find a strange notebook lying in the street that says "Death Note" on it, Light decided it would be a wonderful idea to pick it up. He cautiously took it home. And he wrote a name in it to see if someone would die. When the person did, Light, unlike many others with a high intelligence, decided to keep using the death note. He decided to kill all the criminals in the world, the ones the justice system had left unpunished. After they were all gone, he would become the god of the new world.
I know what you're thinking. He's insane. Isn't it more interesting that way?
The Japanese government quickly figured out that the sudden deaths of numerous criminals was no coinkeydink. They just couldn't figure out how it was happening. So, they hired L, a mysterious detective who can solve any crime. And, like Light, L happens to be a genius, too.
Over all, this series is pretty engaging. Even if you don't like Light because of his...well, desire to be God...you'll probably like L, who has strange mannerisms and a desire for sweets. The thing about this series is that the people in it are so smart. There will be numerous twists that you'll never see coming. You'll have to watch all the way to the end to figure out just going to happen.
Will justice prevail?
You'll have to watch to find out.