Passage Summary: The author argues that because e-books are still just digital versions of paper books, we don't really know what e-books will eventually become or how they will truly function.

Conclusion: We cannot yet fully comprehend the nature of e-books as a medium.

Reasoning: E-books are currently in an initial phase where they merely replicate print content, and a medium's true nature can't be understood until it moves past this stage.

Analysis: The argument relies on a bridge between a medium's 'form' and our 'understanding' of it. To justify this conclusion, we need a principle stating that a medium cannot be understood until it has evolved beyond merely mimicking its predecessor. Look for an answer that explicitly connects the 'ultimate form' of a medium to the ability to 'understand' that medium.