Oh, being an anime fan of course I would set my eyes on this one. It's called Death Note: Another Note and it is a prequel to the popular manga storyline. Actually, it is effectively an elaboration of a murder mystery that came up in the manga series. A warning to all, the book probably makes sense only if you are either familiar with the DN series or are a huge fan of the main character. Fine, the story will make sense but you won't be as enthralled by the plot.
The story falls into the mystery genre where folks are trying to uncover the truth behind some horrid murders. And of course the man of the hour is lovable L, the genius detective of the DN series. You also come across Masori Naomi, the brilliant mystery-solver from the series.