A Greasemonkey script which changes the font family of Kindle Cloud Reader to sans forgetica (Font must be installed locally)

Font Changer for Kindle Cloud Reader

// ==UserScript==
// @name        Font Changer for Kindle Cloud Reader
// @namespace   https://github.com/jcc10/
// @include     https://read.amazon.com/
// @run-at      document-start
// @version     2
// ==/UserScript==

const fonts = `"sans forgetica"`;

async function main() {
  while(true){
    try{
      let reader = document.getElementById("KindleReaderIFrame").contentDocument;
      for(let frame of reader.getElementsByTagName("iframe")) {
        let doc = frame.contentDocument;
        if(doc.getElementById("fontChangerElement")){
          continue;
        }
        var s = doc.createElement("style");
        s.type = "text/css";
        s.textContent = `* { font-family: ${fonts} !important; }`;
        s.id = "fontChangerElement";
        doc.head.appendChild(s);
      }
    } catch(e){
      null;
    }
    await wait(1000);
  }
}

function wait(duration) {
  return new Promise((res) => {
    setInterval(res, duration);
  });
}

main();

I couldn't find any CDNs for sans forgetica, so you have to install it locally.

You can also change the font up at the top.

https://sansforgetica.rmit/