In important ways they are better than traditional books: they save paper and can be reproduced at low cost; users can increase the type size and read while eating, using a finger as a page-turner; hundreds of books can be downloaded from the web. On the downside, they are expensive, difficult to lend, easier to steal and could be destined for oblivion if formats change in the future.
More worryingly, as with so many innovations, manufacturers try to build a walled garden around their products in the hope that they will become the standard for the world. Thus Sony's impressive eBook offers the books Sony wants to sell (without internet access so far) and Kindle, which has been well received despite problems with some screens, aims to sell books that Amazon stocks. That is an extremely large library, and already ebooks account for 6% of Amazon sales of books with dual formats.
Both of these ebooks are only sold in the US at the moment. The main European competitor, the iLiad, is based on open source software (built by volunteers) and has web access, but is more complicated to operate than the others. Users can download anything from the vast free library of Project Gutenberg on the web.
It would be nice to think that ebooks will avoid the format wars between the likes of Apple and Microsoft that have dogged the development of digital music players, but that seems unlikely. An ebook without a proprietary walled garden would offer the best opportunity for books, not least because it could provide an outlet not just for mainstream works but also for self-published books.
This would create an online marketplace in which they could be sampled and voted on by peer groups, as digitised music is. This doesn't mean that the writing is on the wall for the traditional book. Its texture and the ease with which it can be browsed makes it almost perfect for purpose. But in future books will have to welcome a new member to the family with which they will share more similarities than differences.