I’m still thinking — and will be for a long time — about the relationship between the act of reading a book or article or story and many other kinds of “reading” or visual “scanning.” (Earlier posts on this topic are here and here.) When you read a book your eyes scan a page, but do so with a certain regularity, with a linear motion that is only interrupted when you move from the end of one line, at the far right of the page, to the beginning of the next, at the far left of the page. (Assuming you’re not reading Hebrew.) But you know, those are very frequent interruptions of the lines! — though they are predictable, even rhythmical.
The less predictable interruptions come when you need to look at footnotes, which is one reason why books that wish to have a strong narrative momentum don't use footnotes. When I wrote my book Original Sin I wanted readers to experience it as a story, not as a work of scholarship — even though I did a great deal of research while writing it and believe that it is a work of sound scholarship — so rather than using footnotes or even endnotes I placed a “Bibliographical Essay” at the end.
You have to have great narrative skill and tact to produce a story with frequent interruptions of the line. I can think of two people who have done it well. The first is Jonathan Stroud, whose fabulous Bartimaeus books for young adult readers are lightly dotted with footnotes featuring witty and sardonic commentary from Bartimaeus himself. The other is Susanna Clarke, whose Jonathan Strange and Mr Norrell has so many footnotes that you would think they would surely destroy the momentum of the tale. Yet the footnotes, most of which serve to fill in the details of Clarke’s alternative history of England, are my favorite part of the book, and many other have said the same. That was a daring move on Clarke’s part indeed, but a brilliant one, because the footnotes do as much as the story itself to create what Tolkien called a “secondary world.”