If you have the Stylish browser add-on, you can make this book much easier to read with this custom style I wrote: The Art of Unix Programming, and … Usability – improve readability.

Here is the main part of the style’s CSS, if you just want to use your developer tools on each page:

body {
    font-size: 20px;
    line-height: 1.3;
    max-width: 700px;
    margin-left: auto;
    margin-right: auto;
}

I referred to Butterick’s Practical Typography when choosing these numbers.