And we haven’t yet touched on situational disabilities. A situational disability is one in which a person who would otherwise be able to interact with your ebook is in a position in which they can’t, or find themselves facing the same limitations. For example:

• someone trying to read on a cell phone will gain an appreciation for the difficulty of reading small sections of prose at a time, as someone with low vision experiences when reading using zooming software;

• someone attempting to read on their deck on a bright summer day, angling and holding their tablet close to their face to follow the prose, will understand the difficulty experienced by someone with age-related sight loss and/or who has trouble with contrasts;

• someone sitting on the subway going home who has to turn on subtitles in an embedded video to read the dialogue will experience how a person who is deaf interacts with the video.

In other words, everyone will benefit from accessible data at some point in their lives, as there are a lot of ways accessible data improves access that aren’t always immediately obvious. Accessibility is critical for some and universally beneficial for all.

The richer you make your data the more intelligently it can be used; so even though you may not be able to accommodate everyone at the end of the day, you can go a long way toward accommodating the majority with a number of simple measures. And that is the focus of this guide.

Usability as defined here, however, is outside the realm of content production, and can’t be tackled by a guide whose focus is increasing the quality of your content. The EPUB specification bakes in some requirements on the reading system side to improve usability, but not every reading system is going to support every accessible feature, and usability is not just support for EPUB but extends into the design of reading systems themselves.

You can’t let usability influence your accessibility decision making, however. A typical practice is to target the industry-leading platform and build around its capabilities (and deficiencies), but what value does this bring you in the long term? Think of the cost that resulted from making Internet Explorer-only friendly websites when it held 90 plus percent of the market as an example of where following the leader can take you. Your books will hopefully be selling well for years to come, but unless you enjoy reformatting from scratch each time you look to upgrade or enhance, it pays to put the effort into doing them right up front.