I’ve writ­ten a lot about ebooks over the years, but very lit­tle on what makes them read­able. That’s unfor­tu­nate, since the defaults you get with almost every ebook reader pro­vide a sub-​optimal expe­ri­ence. Every time I hear some­one say, “I tried read­ing a book on my iPhone, but I just couldn’t do it,” and I look at their phone, I real­ize that with those set­tings I couldn’t do it either. So let’s go over what makes books read­able in the first place and how to mimic that on your reader of choice.

The first and most obvi­ous aspect of read­abil­ity is of course the type­face you use. The right font can make or break your read­ing expe­ri­ence. Fonts come in two main styles, serif and sans serif. Serif fonts have small orna­men­tal lines, called ser­ifs, that give them a more styl­ized look and more impor­tantly, guide the eye along the line of text. It’s for this rea­son that serif fonts have tra­di­tion­ally been favored by typog­ra­phers for long stretches of nar­ra­tive. Com­mon serif fonts are Times Roman, Geor­gia and even the mono­spaced Courier.

Sans serif fonts tend to be much sim­pler let­ter shapes, as they lack the ser­ifs. This makes them look cleaner on the page or screen, but in the­ory less read­able over time in bulk para­graphs. Sans serif fonts have tra­di­tion­ally been pre­ferred for on screen use because they’re sim­pler to ren­der. Com­mon sans serif fonts include Hel­vetica or Arial, the Verdana/​Tahoma/​Nina fam­ily and the handwriting-​like Comic Sans.

So what’s best for ebook read­abil­ity? That’s not an easy ques­tion. It’s worth not­ing that most peo­ple don’t actu­ally read one let­ter at a time. Instead adult read­ers take in whole words, phrases and even sen­tences at a time. The pat­tern recog­ni­tion on the brain is absolutely cru­cial, and any­thing that dis­turbs or alters the expected pat­terns will dra­mat­i­cally impede the read­ing process. For any­thing longer than a few lines, I pre­fer serif fonts. On a good serif font, the ser­ifs really do guide the eye along the line and make read­ing more com­fort­able. If I’m on a lower res­o­lu­tion device and have to go with a sans serif font, I pre­fer some­thing like Tre­buchet MS, which at least has pseudo-​serifs to dif­fer­en­ti­ate let­ter shapes. Ver­dana, which was also designed expressly for on-​screen read­abil­ity, as well as it’s com­pressed sib­ling Tahoma — and the even fur­ther com­pressed Nina — is another good choice if you need to go sans serif.

So now that we know what kind of font to use, which fonts in par­tic­u­lar are best? While there’s a cer­tain appeal to Times or Times New Roman, the “default” pro­por­tion­ally spaced serif font, it was designed to be printed, and doesn’t always trans­late well on screen. It’s a very nar­row font with com­par­a­tively lit­tle white space between lines, to allow news papers to cram the max­i­mum num­ber of words on the fewest pos­si­ble pieces of paper.

If it’s avail­able, I pre­fer Geor­gia, which was designed for on screen read­abil­ity. It has a taller x-​height than Times, which means the lower case let­ters are taller — and gen­er­ally wider — for a spe­cific point size than Times.It also has lovely ser­ifs that evoke the type­set­ting on vin­tage hard­cov­ers and a clear, script-​like ital­ics version.

If you’re using a newer device with True­Type turned on, Microsoft’s new Cam­bria or Con­stan­tia fonts look even bet­ter than Geor­gia, because they’re designed not only for on screen read­abil­ity, but also to take full advan­tage of sub­pixel font ren­der­ing. Basi­cally, these fonts make it appear that you have three times num­ber of pix­els that you actu­ally have. Cam­bria has a more “infor­mal” feel to it, with rounder let­ter shapes. Con­stan­tia is closer to Times with a lot of straight, ver­ti­cal lines.

Okay, you’ve got the right font, now how big should it be? This is bal­anc­ing act and frankly the hard­est deci­sion to make. It’s depen­dent on sev­eral factors.

First is line length. A good rule of thumb is that you should have on aver­age about six to eight words per line. So if you pick a font that’s too big, you won’t get as many words per line as you should and read­ing will feel very “choppy” as your eye keeps dart­ing back and forth very quickly. (Con­versely, this is why it’s impor­tant to use giant mar­gins or split text into columns on wide mon­i­tors. If the line length is too long, your eye tends to wan­der up or down to other lines before you get to the end and reset.)

But you also need to have a rea­son­able amount of white space. A lot of reader soft­ware will allow you to set your mar­gins. Believe it or not, there’s actu­ally an advan­tage to hav­ing healthy mar­gins around the text. It helps the brain com­part­men­tal­ize the text and keeps the page from look­ing too busy and over­whelm­ing. Try it. You’ll be more com­fort­able with a rea­son­able mar­gin than with text that goes right up to the edges of the screen.

White space is also a func­tion of font choice, as your font will tend to define, at least at first, your ver­ti­cal line spac­ing. One of the rea­sons I like Tre­buchet MS so much is that in addi­tion to being a serif-​like sans serif font, it also defaults to wider than aver­age line spac­ing, with more white space between lines of text. This makes it eas­ier for the eye to fol­low long each line with­out jump­ing above or below and con­fus­ing things. This is also why the lat­est ver­sions of Word default to 1.15x line spac­ing. That lit­tle extra white space really makes a dif­fer­ence in read­abil­ity on screen.

So what’s the answer? It’s going to be dif­fer­ent for every­one. Find a serif font you like and then try dif­fer­ent com­bi­na­tions of mar­gins, font sizes and if you can, line spac­ing until you find some­thing com­fort­able at six to eight words per line. In eReader on my iPhone, that comes to Geor­gia at Medium font size, nor­mal line spac­ing and wide mar­gins. On the iPhone Kin­dle app my options are more lim­ited, so I just go with the sec­ond of the five font sizes. In Stanza, my reader of choice, you can tweak almost every­thing and I have it set up with nearly ideal font, font size, line length and line spacing.

Let’s talk about para­graphs. Most of time, you’ll take what you get. Some books and some read­ers will give you indented para­graphs, like you see in most printed fic­tion, where the line spac­ing doesn’t change but the first line of each para­graph is indented slightly. Oth­ers will give you block para­graphs, where the first line of a para­graph is not indented, but there is a blank line between every para­graph and the next. If you have the option, go with indented para­graphs. They’re no eas­ier nor harder to read than block para­graphs, and they let you fit more on each page, so you turn pages less frequently.

Another point to con­sider at the para­graph level is jus­ti­fi­ca­tion. Here I dif­fer with the con­ven­tional wis­dom. All the stud­ies I’ve read say to go with unjus­ti­fied, or “ragged” right mar­gins, where the let­ter spac­ing is uni­form and each line ends where you run out of words and have no room to fit the next word in the sen­tence. The uni­form let­ter spac­ing makes it eas­ier for your brain to read each word.

In jus­ti­fied para­graphs, the spac­ing between each let­ter or each word is tweaked just enough so that the end of the line makes a straight ver­ti­cal line down the right side of the screen just as the left mar­gin does. Per­son­ally, I like this bet­ter, even if it makes things just a bit harder to read. It looks more like a real book that way. I find ragged mar­gins dis­tract­ing, so for my money, jus­ti­fied is actu­ally eas­ier to read. It helps if your reader pro­gram sup­ports auto­matic hyphen­ation, break­ing big words across lines if they fall at the line end. This means you have vir­tu­ally no instances of the big honk­ing gaps that can occa­sion­ally hap­pen with full jus­ti­fi­ca­tion, big words and shorter line lengths.

Okay, you’ve got all the typog­ra­phy down. What about color? On a lot of phones, you aren’t lim­ited to just black and white. Oddly enough, though, you’re prob­a­bly best off stick­ing with black text on a white back­ground any­way. It offers the best con­trast, which is going to lead to less eye strain. If you want to mimic the warmer feel of a paper book, you can change the back­ground to an off-​white or cream color with­out los­ing much in the way of con­trast. A lot of read­ers allow for inverted col­ors for night read­ing with the lights off, but I find that you’re prob­a­bly bet­ter off just dim­ming the bright­ness to a black on gray that you find com­fort­able. Light text on black doesn’t look very good with font smooth­ing enabled. In gen­eral, I would stay away from other color com­bi­na­tions, and please, never, ever use a graphic tex­ture as your back­ground. A lot of read­ers allow for this, and even make it the default, but it’s just going to dis­tract your eye from the actual text. Yes, it’s very cool that you can make the back­ground look like parch­ment, but don’t do this if you actu­ally want to read the book.

A lot of books will scroll the text for you, like a teleprompter. While this seems like a good idea, in that you can read not actu­ally need­ing to turn the page, I’ve never made it work. My read­ing speed changes depend­ing on the text. Pages with a lot of dia­logue I’ll get too much ahead of the scrolling and get frus­trated because I have to wait, and pages with a lot of descrip­tion or inte­rior mono­logue I’ll have to start skim­ming just to keep up. Stick with turn­ing each page one at a time for max­i­mum readability.

And lastly, we come to all the other stuff your reader pro­gram can dis­play that isn’t the book. Things like title, page num­ber, time, but­tons for all kinds of func­tions: find, anno­tate, book­mark, etc. If you can, keep these to a bare min­i­mum. Every addi­tional thing on the page is some­thing your brain has to rule out every time you see it. On Stanza on my iPhone, I have just the progress bar — a thin line at the very bot­tom of the screen show­ing how much of the book you’ve read rel­a­tive to the total length — and the stan­dard iPhone sta­tus bar at the top. I could even hide the sta­tus bar, but I usu­ally read in bed, and I need to be able to see the time so I know when it’s time to put the book aside and go the heck to sleep if I want to avoid being a zom­bie the next day. Sim­pler is bet­ter, in general.

And that’s it! Now you know enough about typog­ra­phy and how the brain actu­ally reads text to make your ebook read­ing expe­ri­ence as close to or even bet­ter than read­ing a paper book.