The Great Cleaner Upper
This is my plugin for aggressively cleaning the absolute heck out of books. You may enjoy this plugin if your books consist almost entirely of plain text with minimal formatting elements and you don't mind removing most/all CSS.
Because this plugin removes
calibre CSS classes, some of which may be used for simulating bold, italic, headers, blockquotes, etc., you should use find-and-replace to turn those elements into real
<blockquote>, etc. tags before running the cleaner.
BeautifulSoup comes from here: https://www.crummy.com/software/BeautifulSoup