If you’re still waiting for a sign that e-books have arrived in the mainstream of publishing, here it is: Nielsen says it is months, rather than years, away from producing a sales chart for digital editions.

Nielsen is responsible for the most important charts used by the trade. It’s how you know if your book is an official bestseller. It is also the organisation responsible for the ISBN system in the UK.

In an interview with The Bookseller, Jonathan Nowell, president of Nielsen Book, said that the company would not launch a sales chart unless it could obtain reliable figures, and was certain those figures were significant. Yet he said that such a chart is only months away.

How do we interpret this? Clearly e-book sales are significant enough to warrant this activity.

Nowell also mentioned that it’s important that publisher assign separate ISBNs to their e-book editions, rather than using the same ones they give to the print editions.