When you collect comics, there are all sorts of factors that determine the value of the book. Certain important comics (they’re referred to as “key” issues) are high-value. So, for instance, Detective Comics #358 isn’t worth all that much, but issue #359 is, because it’s the first appearance Batgirl. (Actually, it’s the first appearance of the Barbara Gordon version of Batgirl—but never mind that for now.) And first-appearances, or first-cover appearances, or origin-stories, tend to be worth a lot.
Another factor is the condition of the comics. The better the condition, the more valuable they are. A third factor is whether or not the comic has been professionally graded by one of the three major grading consortiums. A fourth factor is pedigree: Believe it or not, certain individual books hail from landmark collections and if you can prove that your copy of Detective Comics #359 is from, say, the Mile High Collection or the Hawkeye Collection—both of which are notable in comics lore—then it becomes even more valuable.
