Download your Kindle Highlights to local markdown files. Great for Obsidian.md.

kindle.rb

#!/usr/bin/env ruby

# gem install active_support
require 'active_support/inflector' 
require 'active_support/core_ext/string'

# gem install webrick (only ruby3) 
require 'webrick' 

# gem install mechanize
require 'mechanize'

# set this variable to https://read.amazon.ca if you are in Canada (or likewise elsewere)
root_url  = ENV['KINDLE_URL'] || "https://read.amazon.com"
login     = ENV['KINDLE_USER'] || raise("Need KINDLE_USER env var")
pass      = ENV['KINDLE_PASS'] || raise("Need KINDLE_PASS env var")

 
output_dir = if ARGV[0].nil? or !File.directory?(ARGV[0])
  STDERR.puts "#{File.basename(__FILE__)} [valid output directory]"
  exit(1)  
else
  File.expand_path(ARGV[0])
end

m = Mechanize.new
m.user_agent_alias = 'Mac Safari'
m.cookie_jar.load("cookies.yaml") if File.exist?("cookies.yaml")
at_exit {  m.cookie_jar.save("cookies.yaml", session: true) }

response = m.get("#{root_url}/notebook")

if form  = response.form("signIn")
  # attempt to login
  form  = response.form("signIn")
  form.email = ENV['KINDLE_USER']
  form.password = ENV['KINDLE_PASS']
  response = m.submit(form, form.buttons.first)
end

if response.title != "Kindle: Your Notes and Highlights"

  STDERR.puts "Unexpected page. Additional security or captcha? Check your phone."

  file = File.open('/tmp/amazon.html', "w+") do |f|
    f << response.body
  end

  STDERR.puts "Inspect: #{file.path}"
  exit(1)
end

# Get all books
books = response.search("div#kp-notebook-library").children.select { |child| child.attributes["id"].present? }

# Write each out as formatted markdown file to 
books.each do |book|
  full_title = title = book.children.search("h2").first.text.squish

  # If the book title has a colon in it we terminate the title there
  title = $1 if title =~ /^([^\:]+)\:/

  filename = title.strip.gsub(/[^\w]/, '_')
  filename = title.parameterize(preserve_case: true, separator: '_')

  puts "* writing #{title} to #{filename}.md"
  
  File.open("#{output_dir}/#{filename}.md", "w+") do |f|

    asin = book.attributes["id"].value.squish
    author = book.children.search("p").first.text.split(":").last.strip.squish

    # Write markdown header

    f.puts "# #{full_title}"
    f.puts " by [[#{author}]], asin: [#{asin}](kindle://book?action=openasin=#{asin})"
    f.puts " #Book"

    highlights = m.get("#{root_url}/kp/notebook?captcha_verified=1&asin=#{asin}&contentLimitState=&")
      .search("div#kp-notebook-annotations").children
      .select { |child| child.name == "div" }
      .select { |child| child.children.search("div.kp-notebook-highlight").first.present? }

    highlights.each do |highlight|
      text = highlight.children.search("div.kp-notebook-highlight").first.text.squish
      location = highlight.children.search("input#kp-annotation-location").first.attributes["value"].value

      # Write markdown highlights
      f.puts
      f.puts "---"
      f.print "#{text}"
      f.puts " - location: [#{location}](kindle://book?action=open&location=#{location}&asin=#{asin})"
    end

  end
end

This is great. Another tool that gets the job done is Readwise and their Markdown exporter.