"today, for titles that have a Kindle edition, Kindle book sales are 48 percent of the physical sales."
That sounds really great: however, how much percent of the books have a Kindle edition ?
In addition to that, more importantly, this is only within the Amazon audience: I bet a lot more Amazon customers fall into the eBook audience than the average audience of bookstores. But by stories like these, a lot of people will be made aware of the success of the eBooks, and will be afraid of missing out on something.
However, over here in The Netherlands, some numbers were released today: 60,000 eBook sales in 2009. Compare that to the total of 50,000,000 books sold, and you can see eBooks still account for about 0.1% of the total book sales. Hardly comparable to the "48%" named in the article.