download your copy of epub/mobi of caltech fenman lecture on physics vol i http://www.feynmanlectures.caltech.edu/I_toc.html, powered by https://github.com/lepture/getbook/

feynman-lecture-vol-i.json

{
  "uid": "feynman-lecture-vol-i",
  "title": "The Feynman Lectures on Physics, Volume I",
  "author": "Richard Feynman",
  "chapters": ["http://www.feynmanlectures.caltech.edu/I_89.html","http://www.feynmanlectures.caltech.edu/I_90.html","http://www.feynmanlectures.caltech.edu/I_91.html","http://www.feynmanlectures.caltech.edu/I_92.html","http://www.feynmanlectures.caltech.edu/I_01.html","http://www.feynmanlectures.caltech.edu/I_02.html","http://www.feynmanlectures.caltech.edu/I_03.html","http://www.feynmanlectures.caltech.edu/I_04.html","http://www.feynmanlectures.caltech.edu/I_05.html","http://www.feynmanlectures.caltech.edu/I_06.html","http://www.feynmanlectures.caltech.edu/I_07.html","http://www.feynmanlectures.caltech.edu/I_08.html","http://www.feynmanlectures.caltech.edu/I_09.html","http://www.feynmanlectures.caltech.edu/I_10.html","http://www.feynmanlectures.caltech.edu/I_11.html","http://www.feynmanlectures.caltech.edu/I_12.html","http://www.feynmanlectures.caltech.edu/I_13.html","http://www.feynmanlectures.caltech.edu/I_14.html","http://www.feynmanlectures.caltech.edu/I_15.html","http://www.feynmanlectures.caltech.edu/I_16.html","http://www.feynmanlectures.caltech.edu/I_17.html","http://www.feynmanlectures.caltech.edu/I_18.html","http://www.feynmanlectures.caltech.edu/I_19.html","http://www.feynmanlectures.caltech.edu/I_20.html","http://www.feynmanlectures.caltech.edu/I_21.html","http://www.feynmanlectures.caltech.edu/I_22.html","http://www.feynmanlectures.caltech.edu/I_23.html","http://www.feynmanlectures.caltech.edu/I_24.html","http://www.feynmanlectures.caltech.edu/I_25.html","http://www.feynmanlectures.caltech.edu/I_26.html","http://www.feynmanlectures.caltech.edu/I_27.html","http://www.feynmanlectures.caltech.edu/I_28.html","http://www.feynmanlectures.caltech.edu/I_29.html","http://www.feynmanlectures.caltech.edu/I_30.html","http://www.feynmanlectures.caltech.edu/I_31.html","http://www.feynmanlectures.caltech.edu/I_32.html","http://www.feynmanlectures.caltech.edu/I_33.html","http://www.feynmanlectures.caltech.edu/I_34.html","http://www.feynmanlectures.caltech.edu/I_35.html","http://www.feynmanlectures.caltech.edu/I_36.html","http://www.feynmanlectures.caltech.edu/I_37.html","http://www.feynmanlectures.caltech.edu/I_38.html","http://www.feynmanlectures.caltech.edu/I_39.html","http://www.feynmanlectures.caltech.edu/I_40.html","http://www.feynmanlectures.caltech.edu/I_41.html","http://www.feynmanlectures.caltech.edu/I_42.html","http://www.feynmanlectures.caltech.edu/I_43.html","http://www.feynmanlectures.caltech.edu/I_44.html","http://www.feynmanlectures.caltech.edu/I_45.html","http://www.feynmanlectures.caltech.edu/I_46.html","http://www.feynmanlectures.caltech.edu/I_47.html","http://www.feynmanlectures.caltech.edu/I_48.html","http://www.feynmanlectures.caltech.edu/I_49.html","http://www.feynmanlectures.caltech.edu/I_50.html","http://www.feynmanlectures.caltech.edu/I_51.html","http://www.feynmanlectures.caltech.edu/I_52.html"]
}

get_urls.js

Goto = (vol,chap,sec) => {
    var volstrings =["I","II","III"];
    var dest;
    var chapstr = "0"+String(chap);
    chapstr = chapstr.substr(chapstr.length-2);
    dest = volstrings[vol-1] + "_" + chapstr + ".html"
    if(typeof(sec)!=='undefined') {
        dest += "#Ch" + String(chap) + "-S" + String(sec);
    }
    return (dest);
}

$('a.chapterlink').toArray().map(a => 'http://www.feynmanlectures.caltech.edu' + eval(a.href.split(':')[1]))

For anyone who comes across this thread (as I just did), to fix this just:

pip install beautifulsoup4==4.6.0