Moggleberries
I have one, what's this vol. 13 thing everyones going on about? That's the information volume. It pretty much gives the statistics of each character, information about understanding the story, design concepts for each character, explaining how the death note works and the rules, some games and 4komas, and it also includes the pilot chapter. The Pilot chapter being what Death Note was originally based off of.
Oh, and it comes with L's true name card.
It's pretty sweet, I got a copy at Anime Boston. Too bad I can't read it
gonk It's supposed to come out in English sometimes early next year(February I think?).
Also, to answer about how many episodes the anime version is, there are currently 37. But I heard that theres gonna be a short animated special that'll come out in the coming months to wrap up what happened after(not 100% on that one though....).