A traditional book encourages the reader to take a direct path from beginning to end. Pages are arranged in a fixed order and numbered. But there are many cases where a book is not read in the order of its pages. Imagine Mary, who consults her textbook to understand a particular physics principle. She looks up the name of the principle in the index, and then turns directly to that page. After reading the description, Mary realizes that she doesn’t understand. She flips the pages to earlier in the textbook where she remembers a key related concept was first introduced.

Instructional texts are not the only contexts where you might want to navigate non-linearly. James is reading a crime novel. He reads a few pages, and then, as he always does, flips to the last chapter to see how the story ends. He finishes reading the book, remembers a part that he particularly liked, and then flips back to re-read it.

Digital technologies have opened up new possibilities for facilitating the way we navigate through texts. If Mary were reading a digital book, a search for the concept she does not understand might return a variety of relevant information: where the concept is first explained, what she needs to know to understand the new concept, and where that concept is later used in the text. The book could recommend, based on her knowledge, which content she should view first. Using hyperlinks, it is now possible to easily jump between different parts of a book, and using adaptive recommendations, a system can indicate which parts of a book are most relevant to a particular reader.

If James were reading a digital book, the possibilities of new technology suggest a more interactive and more personalized reading experience. The author could indicate multiple ways a book could be read to suit different preferences. For James, the book could be automatically reordered to present the final chapter first. Based on James’ reading behavior, the book could automatically infer which parts James liked the best, and link back to those parts at the end of the book.

To facilitate multiple paths through a book, there are several considerations related to technology and user experience design: semantic indexing, designing for non-linear navigation, making intelligent recommendations, and adaptive reconfigurations.

Semantic indexing. At a minimum, the content of the book needs to be indexed (either through natural language processing technologies or crowdsourcing) so that semantically meaningful links between different parts of the book can be made.

Designing for non-linear navigation. With non-linear navigation comes the need to design the book’s interface to support the user in taking multiple views of the text. Side-by-side split screen views should be facilitated so students can make direct comparisons between content. Reading history should be saved so the reader does not lose the page they were interested in, and can retrace their steps through the book if necessary.

Making intelligent recommendations. As the number of navigation paths increase, the reader may need recommendations for which path to view next. The quality of these recommendations depends on how effectively the book can construct a reader profile, interpret reading history, and understand how its contents can meet the reader’s needs.

Adaptive reconfigurations. For an engaging reading experience, a book could adaptively reconfigure its contents based on reader reactions and preferences. Using different navigation paths, writers could author multiple reading experiences within a single book, tailored toward different profiles.

One final consideration in this discussion is ensuring that these adaptive technologies support how readers perceive their own needs. In general, users want to maintain control when interacting with technologies. For this reason, recommendations may be better received than adaptive reconfigurations. Readers will want to be able to understand how the book is being reconfigured and potentially select their own path. As adaptive technologies become more sophisticated, the goal should be to enable the reader to make more informed choices about how and what they read.