Adobe has revealed its plans for the latest version of its server software for distributing eBooks, which will be released on September 22 and called Adobe Content Server 4. The most important improvements are the new support for the EPUB format, as well as a pay-as-you-go pricing model that charges based on the number of downloads.

As a consumer, I remain unenthusiastic about eBooks, but Adobe trotted out some encouraging statistics on this front, saying that the Association of American Publishers reports steady “double digit” increases in eBook sales, and that eBook sales make up 20 percent of technical publisher O’Reilly Media’s revenue.

Content Server 4 certainly sounds like an improvement. One of the most promising aspects of eBooks is the ability to read on multiple devices, including your personal computer, specialized readers like Amazon’s Kindle and the Sony Digital Reader (Adobe supports the latter) and smartphones. By supporting the “flowing” EPUB format, which can readjust the text depending on your device (as opposed to PDFs, whose format is more locked-in), Adobe is taking advantage of this trend.

The other question is whether digital rights management (DRM) that restricts how books can be used and shared is the way to go. Adobe’s spokespeople argue that the publishing industry is better-suited for DRM than the music industry, where the technology hasn’t been terribly popular — Amazon’s music service, for example, has done well by offering MP3s without DRM. But then, Adobe has a horse in the race, since the big selling point of the Content Server is its management of DRM licenses. It’s worth noting that O’Reilly, one of the success stories that Adobe itself offers as an example, provides its books without DRM.