This JavaScript one-liner iterates through all of the paging and "add to cart" buttons at promo.comixology.com to add each of 723 Marvel #1s to your Comixology cart. Checkout and login etc. are still handled manually. I just pasted this into my Chrome console.

Marvel #1 Add All

pagers = document.getElementsByClassName('adHocPager');
for (i = 0; i < 18; i++) {
  add_buttons = document.getElementsByClassName('addComicLink');
  for (a = 0; a < add_buttons.length; a++) {
    if (add_buttons[a].text != 'In Cart') {
      add_buttons[a].click();
    }
  }
  for (p = 0; p < pagers.length; p++) {
    next_buttons = pagers[p].getElementsByTagName('a');
    next_button = next_buttons[next_buttons.length - 1];
    next_button.click();
  }
}