Notes on readable typography
Good typography is mostly invisible. Readers should notice the words, not the layout.
Line length
Aim for roughly 60 to 75 characters per line. Longer lines make it easy to lose your place when moving to the next one.
Spacing and size
A line height around 1.5 suits body text, and a base size of at least 16 pixels keeps it comfortable on small screens. Leave generous space between paragraphs and headings.
Contrast
Make sure text stands out clearly from its background, and offer a dark variant for people who prefer it. Both are simple to do with a few lines of CSS.