Simon Rowberry

I was invited to give a talk for the Centre for the History of the Book at the University of Edinburgh. I took the opportunity to talk through some of the methodological challenges facing researchers of ebooks.

I’ve been seriously working on research for my history of the Kindle for a couple of years now and I’m still figuring out how to capture the impact of the Kindle on the scale of both the publishing/technology industry and the individual reader.

This tension is clearest when looking at the available data on reading and the shared highlights. There are a large number of individuals making personal choices behind the 500,000 shared highlights of a single edition of Wuthering Heights. If we scale this to over 4 million ebooks and 40 million Kindle users, it becomes extremely difficult to focus on both the local and global trends (and doubly so when access to the data is obsfucated and entirely unavailable): What counts as an appropriate sample? To what degree can individual highlights link to the mass of activity? How much data can I even get hold of?

While I ponder these questions, there’s still the problem of method. In order to figure this out, here’s a pilot study of the Harry Potter series as a complete unit that is manageable yet has received a fair amount of attention.

On the global level, shared highlights might not be able to tell us much about readership because an unknown number of readers choose not to highlight or share their efforts. The benefit of using Harry Potter, however, comes from the fact it is possible to gauge popularity across the series.

In recent versions of the Kindle software, a helpful pop-up box appears “About This Book” when opening a title for the first time. Luckily, this pop-up contains the total number of shared highlights and how many unique sections of the title have been highlighted. (These may not necessarily be up-to-date, but all the data here comes from 20 October 2015)

The data from the Harry Potter series reveals some interesting patterns. Figure 1 shows the total volume of shared highlights for each title, while figure 2 looks at the number of unique highlights per title. The most striking part of figure 1 is that the visible highlights (the top 10 most shared highlights) barely represent 10% of all shared highlights for any individual title.

Figure 1.  Total highlights for each Harry Potter title and the visible top 10 highlights (click for full size)

Figure 2. Unique highlights for each Harry Potter title (click for full size)

While the two graphs appear to show that the popularity of the series drops at the end and plummets after the first novel only to be pick up towards the middle, there is a far simpler explanation: the longer books receive more highlights as there is more text to highlight.

The only notable exception is Harry Potter and the Philosopher’s Stone, where more readers are focusing on particular passages. The large increase in total highlights without a similar increase in unique highlights likely indicates that more people are reading the first book than the rest of the series, or at the very least, they lose enthusiasm after the first book.

The second macroscopic view we can get from the Popular Highlights is the location of the shared highlights. Jordan Ellenberg has coined the Piketty Index as a way of using popular highlight locations to see how far through a book a reader got before quitting. From the evidence I’m gathering, it looks like the top 10 shared highlights are more likely to appear at the beginning of a book than the end, but what about the Harry Potter series?

Figure 3. Top 10 Shared Highlights for each Harry Potter title (click image for full size)

As a series, readers are more likely to highlight passages at the end of the book than the beginning. Not only does this suggest that readers are likely to finish the books, but through looking at the content of the highlights from the end of the book, it is clear that some of the most popular parts of the titles are Dumbledore’s speeches to Harry and the denouement of the narrative. Given the make-up of Rowling’s series and the slow start of most of the books, this inversion makes sense.

And that’s about as much as you can deduce from looking at the global level as far as I can tell. Once I’ve dug into the more traditional annotations and highlights of individual readers, I’ll compare the results with the broad patterns identified here.