E-book apps and their typography

Open the same novel in four e-book apps and you will read four different pages. Same words, different type: tighter lines in one, a justified block in another, margins nobody chose. An EPUB is HTML in a zip file, and every line of it is set, at the moment you turn the page, by software following someone’s rules. The useful question about ebook reading apps is whose rules those are.

It matters because typography is not taste all the way down. Some of it is taste — serif against sans, warm background against white — and an app can be forgiven for shipping opinions about that. But underneath the taste sit a few variables with actual evidence attached: how far apart the letters sit, how far apart the lines sit, how long a line runs before it breaks, and whether the spacing between words is allowed to stretch so that both edges come out straight. Those four decide how hard a page is to get through, and they decide it differently for different readers.

The mechanism behind the first of them is crowding: letters interfere with the recognition of their neighbours, the interference grows with distance from fixation, and pushing characters apart attacks it directly. Increased letter and line spacing has been found to improve reading speed and accuracy in dyslexic children with no training involved — one of the few typographic claims with respectable controlled support. Line length is about place-keeping: the return sweep at the end of each line is where readers lose their position, and a shorter measure means fewer, shorter sweeps.

Justification is the quiet one. On a wide printed page, with hyphenation done carefully, a justified block is handsome and harmless. On a narrow phone screen, with hyphenation off, the same setting stretches the spaces between words unevenly — wide on one line, tight on the next — and word spacing is exactly what a reader’s eye uses to plan its next landing. Ragged-right keeps the spacing constant. It looks less like a book and reads better on glass, and most apps default the other way.

Screens complicate the picture further. E Ink panels render grey by dithering and refresh slowly, which is why the e-reader vendors ship weight and sharpness controls that phone apps never need, and why a face that looks right on a phone can look anaemic on a paper-like display. There is no one correct setting to copy from a friend. There is a correct process: change one variable, read something real, and keep what survives.

The controls, ranked

• Letter and line spacing. The pair with the strongest evidence behind them, because they act on crowding directly. If an app exposes only one group of controls, it should be this one — and many expose line spacing while quietly omitting letter spacing.
• Measure. Line length, set through margins or column width. Shorter lines mean fewer place-keeping errors at the return sweep — the argument is laid out in keeping your place on the line — and on a tablet held at reading distance the default measure is usually too long.
• Justification and hyphenation. A single toggle, ideally set to ragged-right. If an app insists on justifying, it owes you hyphenation to keep the word spacing sane, and several don’t pay.
• Typeface. Genuinely the least important of the four. Controlled comparisons of dyslexia-specific typefaces have generally not shown them beating a well-spaced ordinary sans-serif; much of what a special face delivers is spacing you could apply to a face you already like.

The field, app by app

A survey like this has a short shelf life. Apps change their settings screens without notice, the e-reader and the phone app from the same company differ, and a control can exist but hide three menus deep. What follows describes the shape of things at the time of writing, on the versions we checked, and is offered as a map rather than a verdict. E-reader typography is a moving field, and mostly moving in the right direction.

The pattern in the table is worth stating. Kindle gives you the popular controls in coarse steps — enough for comfort, not enough to chase a specific spacing. Kobo is the most generous of the mainstream vendors, with sliders where others have steps and an explicit justification switch, which is presumably easier when you also make the hardware. Apple Books has the strongest opinions and the shortest settings screen: a beautifully set page you are largely not allowed to argue with.

The open-EPUB apps — Thorium Reader, KOReader, the Calibre viewer — expose nearly everything, letter spacing included, and the best of them let you write your own stylesheet and be done with it. They are also, not coincidentally, the apps built closest to the accessibility community, where these controls are treated as requirements rather than preferences. If you need a specific typographic setting rather than a nicer default, this is the family that will give it to you.

A beautifully set page you are not allowed to argue with is still an argument you lost.

The lock-in, stated plainly

Why the publisher wins fights it shouldn’t

An EPUB ships with its own stylesheet. That is by design — the format is web technology, and publishers use it to set the book the way they set the print edition, embedded fonts and all. The reading app then has to decide, property by property, whether your setting beats the book’s. Apps mostly duck the decision. They override font size, usually the typeface, sometimes line spacing, and let the publisher keep the rest — and a “publisher default” switch shifts the whole question back off the app’s desk.

There are honest reasons. A stylesheet that overrides everything will wreck the cases where layout carries meaning — verse, tables, code, drop capitals — and the app takes the blame for the wreckage. But the effect is that the loudest stylesheet wins, and the loudest stylesheet was written by someone who has never met you. When a reader needs wider spacing to make the page legible, “the designer preferred it tight” is not a reason a serious reading tool should accept. The fight should default to the reader and make exceptions for the poetry, not the other way round.

The trade we make instead

Our own position in this field is easy to state and slightly awkward to defend. The app parses EPUB on your device and then throws the typography away entirely. No measure, no margins, no justification, no line — one word at a time at a fixed point, with empty field around it. The spacing question is not answered so much as deleted: crowding has no flankers to work on, and there is no line to keep your place on, because there is no line.

Stated honestly, that is not a victory in the typography argument; it is leaving the room where the argument happens. The publisher’s design carried real information and we discard it — the shape of a stanza, the structure of a table, the visual hierarchy of a chapter — and a reader who wants to sit with a well-set page should use an app that sets pages well and hands over the controls. What we offer is the limiting case, useful precisely when the page itself, however well set, is the thing in the way.

For everyone else, the advice is unglamorous. Find the typography screen in whatever app you already use and spend five minutes in it: push the line spacing up a step, pull the measure in, switch justification off, and read a full chapter before you judge. If the app turns out not to offer those controls at all, that tells you something about who it was set for — and the books, unlike the settings, will mostly move with you.