If the death note anime didn't exist this movie would have a slight chance of being good. Every single character is almost completely changed. Light is just a kid who obtained power and has a childish imagination like L said in the original. It was so easy for L to discover who light was because of how stupid light was. Mia is completely different. All she wanted was to get the book for herself. She didn't care about Light at all and wrote his name down in the book.
Only watch this movie if you want to see how bad it is