Its not an anime or a comic. ITS A NOVEL. But its based on the death note series. It's a prequel to Death Note that mainly focuses on L solving one of his earlier cases. This is pre-Kira and there are no Death Notes (to my knowledge). The story is narrated by Mello. I think the only characters from the Death Note anime/manga in the novel are L and Naomi Misora the chick that was married to the FBI agent that Kira killed, and that later got killed.

Here's a good review and synopsis: http://www.animenewsnetwork.com/review/death-note-another-note-the-los-angeles-bb-murder-cases/novel

And if you want to buy it, Amazon has for around 12 bucks (USD) I think.

I read this a couple of months ago and really enjoyed it! Easily finish-able in one sitting, and the novel itself isn't very... heavy or anything, but a very enjoyable piece of light reading. Really great characterization when it came to Ryuuzaki, too.

Plus the pages felt all smooth and nice *_*