In a press release last week, Amazon announced that it will launch Kindle Singles. This is how they describe what they want.
"compelling ideas expressed at their natural length. Kindle Singles, which can be twice the length of a New Yorker feature or as much as a few chapters of a typical book might be the perfect, natural length to lay out a single killer idea, well researched, well argued and well illustrated--whether it's a business lesson, a political point of view, a scientific argument, or a beautifully crafted essay on a current event. Kindle Singles will have their own section in the Kindle Store and be priced much lower than a typical book."I'll let you know if I find out more...but it could be a very interesting new market