E-Book Universe: Click for full-size version. Download annotated PDF below.

The buzz around Amazon’s Kindle electronic reader has sparked growing interest in digital books, and the universe of players in this space is growing rapidly. New reading devices and content partnerships are announced on an almost weekly basis.

To keep track of it all, we here at TechFlash have mapped out the known universe of e-books -- spanning content, devices, mobile apps, wireless providers, acquisitions, and more. We invite you to take a look, give us feedback, and let us know if we've missed anything. We'll be updating this chart on a regular basis.

To drill down into the topic, here's an annotated PDF of the graphic with embedded links to news stories and other information. It's a large file, but a good way to explore the subject further: PDF, 4.6 MB

The industry is changing rapidly. In recent weeks, we've seen Sony announce a new lineup of electronic readers; bookseller Barnes & Noble form partnerships with forthcoming e-readers from Plastic Logic and Irex; and Google team up with various devices to distribute digital titles from its giant book scanning project. Looming over all this is Apple, which is rumored to be developing a tablet computer with e-reading capability. Apple’s entry into the market ­— given the company’s success with the iPhone and other consumer electronics — could shake things up for Kindle and other players.

Will the bets these companies are making pay off?

Electronic book sales have been growing at a rapid clip, from an estimated $20 million in 2003 to $113 million in 2008, according to the Association of American Publishers. But e-book sales are still relatively small compared with the rest of the book industry — making up less than 1 percent of the $24.3 billion in total book sales last year. With sales still relatively modest, it will be interesting to see if the market can support the growing number of e-book devices and players.

Contributing: Todd Bishop. Follow my updates on Twitter.