One of the blogs (in the sense that I don't actually know the person) that I've recently been visiting is Self Publishing. If you're interested in what happens behind the scenes (aside from actually writing a book), it's a great read.
Anyway, the recent entry talks about Bowkerlink, an online software used to keep track of books. What's interesting is that Morris mentioned ASIN.
Now I'm familiar with ISBN and ISSN. The former is for books and it's your best friend when ordering them, especially considering books come in various shapes and formats (Hardcover or paperback? American or European? Newsprint or acid-free paper?). The latter, on the other hand, is important for any serial publication (such as magazines or comics). And you'll need either one if you expect National Bookstore to carry your title.
Anyway, back when I was still ordering books from A Different Bookstore (they're on sale right now, by the way), one method I'd use to check if they have a certain book available was by browsing through Amazon. Of course below ISBN I'd see another code: ASIN. And you know what, it's only now that I figured out what it is.
ASIN is apparently Amazon's own internal code for their items. And nearly identical to the book's ISBN. Of course that little fact probably doesn't matter but hey, I'm a Bibliophile Stalker!