But I thought it might be worth putting some rigour – ie numbers – around some of the assumptions. So I wheeled out my trusty version of Excel and decided to put its graphing abilities to good use. I wanted to see how rapid the rise (or fall) in page length was over the course of novel series that became suddenly successful.

The four series I chose to graph were:

• Twilight – Stephenie Meyer
• Harry Potter – J. K. Rowling
• the Mars Trilogy – Kim Stanley Robinson
• Lord of the Rings – J. R. R Tolkien

Here’s what the results look like.

I included the last two as controls (and because, you know, they were close to hand). I considered including Asimov’s Foundation books as another (of which there are seven, not including his expanded Empire and Robot series and novels written by other authors). But for the record, Foundation, first published in 1951 in book form totalled 255 pages. The last in the series was Forward the Foundation, which was published 42 years later and came in at 464 pages.

All comparisons are between consistent editions.

For the record:

• the first Twilight book was 434 pages and the last was 736
• the first Harry Potter book was 223 pages and the last was 607 (book five peaked at 766 pages
• the first Mars book was 519 pages and the last was 609.
• the first Lord of the Rings book was 427 pages and the last 416

But here’s where it gets tricky – and probably why the post is titled the Meyer Imperative rather than the Potter Principle. Rowling pulled back on the length of books six and seven. So to adequatelty compare we need to plot all series as if they went to seven books. Enter Excel.

At seven books apiece the last Harry Potter book was 2.7 times the length of the first one. But if the Twilight series had continued in the same pattern, a seventh book in the series would have come in at whopping 1306 pages. And that length would have made in a smidgen over 3 times the lenth of the first book.  A seventh Mars book (Muave Mars, anyone?) would have only clocked in at 828 pages.

So, ladies and gentlemen, we have a winner.

But what’s it all mean, I hear you ask. Who knows? I suspect that publishers who find they’ve got a massive hit on their hands let writers have a freer hand – not necessarily to keep them happy but more likely I suspect to get the product to market faster.

And it isn’t by definition a comment on quality – and certainly I haven’t read the Twilight books – but it will be interesting to see what happens with the next series from Rowling and Meyer, whether they’re a success or not quite so much. And what that means for lengthas the series progress.