The arguments were the same when MP3 players came out surely?
Let me explain to you a few reasons why the two are not comparable:
1. The format that music comes on does not fundamentally alter the experience of using it. Whilst album art etc was nice, once the CD was in your hifi there's no difference between it and an MP3. Reading a book and an ebook, however, are noticeably different experiences. People enjoy the physical action of reading a book, an experience that an ebook reader does not exactly replicate.
2. If you wanted to listen to music on the move you always had to spend a decent chunk on a Walkman, Discman or mini Discman. The 'start-up' cost was always high. To move from using CDs to MP3s was thus an easy move when your existing Discman became damaged or tatty - people were expecting to pay that much on a replacement. Indeed, it was not until the price of MP3 players became closer to that of the existing technology, mini-discmans, that they really became popular. The cost of the existing technology in this case, a book, is many multiples more than that of the 'new' technology, e-book readers.
3. People are used to replacing and refreshing their music collection. How many people have the same song on tape, CD and now MP3? Equally, how many people have bought the same book more than once - the culture isn't there.
4. MP3s and MP3 players are less susceptible to damage than CDs and Discmans, which represents a positive attraction for some. With ebook readers, the situation is the opposite. Ebook readers are more likely to be damaged and broken than the, comparatively robust, book.
So there we have four reasons: experience, price, culture and robustness. There are many more, but I'm sure you agree by this point that a comparison with the transition from CDs to MP3 simply doesn't hold water.