This was recently driven home while laying out the print version of What Fates Impose. I had read some advice about never using single or double spacing. Instead, the advice was to make the line height approximately 115% to 120% of the font height. The advice had come with some pretty obvious examples, so I was sold on the concept.
It is worth noting that I did not go back and look at my prior print layouts at this point.
So after getting the text in place, I selected the “body text” style, and changed it from the default of single-spacing to proportional 120%.
It looked horrid. The lines were so far apart that it made reading comprehension difficult. I tried printing a page in case it was the monitor. Same problem. So I tried proportionate line spacing of 115%. Then 110%. Then 105%.
There was simply too much space between the lines.
I knew the principle held; I’d seen live examples of it. So what was I doing wrong?
tl;dr: It wasn’t me. It was the font I was using. I like Dolous SIL – it’s a nice serif font, under the open font license, and has that kind of seriousness that a good serif should have while not screaming ”I’m a student paper done in Times New Roman.”
What I didn’t realize is that Dolous (at least, the particular version I have) is a “loose” font. There is a large amount of space built in for all the diacrits in different languages and typefaces. Or in other words, the height of the Roman alphabet characters do not make up the entire height of the font. The font itself has a little bit of “padding” – so when I selected “100%”, it provided about as much white space as “115%” with a tighter serif font.
Ultimately, this reinforces the importance – and desired invisibility of good design with your books in any format. There is no magic number, proportion, or rule. There are principles – such as the desired amount of whitespace to make a book readable on screen or page – that these guidelines help point us toward.
But they are guidelines.