Today CourseSmart, a joint venture of five of the biggest textbook publishers, is launching an iPhone app to augment its Web subscription service for eTextbooks. Its subscription service offers access to more than 7,000 textbooks, at an average of 50% off print prices. Currently, CourseSmart has a few hundred thousand student subscribers, out of a potential addressable market of 13 million US college students (they only target higher education, not K-12, for now).

The iPhone app is nice, with a snappy thumbnail browse feature. It's not something you'd read on, per se, but offers easy access to look up something, search for something, or access your notes. Having the option of mobile access will undoubtedly increase the appeal of CourseSmart's subscription service, assuming the company is successful at marketing the new feature.

Currently, CourseSmart's content isn't integrated into the Kindle or other dedicated reading devices; this app marks its first move into increasing access to eTextbooks on any kind of mobile device. Maintaining print-identical formatting and pagination is a crucial aspect of its product; eReading devices aren't ready to support this type of content yet, but the iPhone is a move that makes sense.

The app is significant, too, for what it implies about Apple's intentions (or lack of) for entering the eBook space itself. Apple's recent approval of this app refutes the rumors about Apple killing eBook apps categorically. We still think, though, that Apple could easily add ePub file support to the iTunes store, and in doing so, become a huge player in the eBook market overnight, which would render many eBook apps unnecessary. (CourseSmart doesn't use ePub format; it has its own proprietary image-based format.) For now, though, CourseSmart has a big head start in the eTextbook market, one that other eBook sellers like Amazon don't come close to matching.