Death if you write the name... Insane... Inhuman...
And before Light could suppress the thought: And bears testing.
He quickly dismissed it as the random ramblings of his head. How was the notebook even supposed to work in the first place? Magic? That strained credulity beyond possibility. It was just some prank. On whom, though... was another matter. And what, exactly, would anyone accomplish with this?
If I had made this notebook as a prank... what would've been my objective?
The first answer that sprang to mind would be to prove that people are selfish and would murder anyone who inconvenienced them. But Light thought that was probably just his regular train of thought catching up with him. In fact, there was a surprise: since he picked up the notebook at school, he hadn't yet had a single thought of how humans were inefficient at being moral. Not directly, anyway. Interesting.
He spent ten minutes chewing on his lips until he gave up, sat on his desk chair and stared at the notebook. Tentatively, he opened it and flipped past the first page. All other pages were just regular notebook pages. He picked a pen and... waited. That would be murder, if it worked.
Don't be silly, his common sense said. Such things don't exist. It couldn't possibly work. You'll just write someone's name, nothing will happen, and then tomorrow someone will come to you and ask for the notebook, and then they'll point at you and say you're a horrible person. "You actually wrote a name in this!"