There are no standards when it comes to pirated books. Some of the books are DIY-scans, and some are purchased eBooks with the DRM removed. It all depends on if the publisher has made an electronic version and if someone is willing to part with money and time to make it available. DIY-scans can range from a bad photocopy that looks like a CAPTCHA test to a perfect scan run through high-end OCR software that is searchable and crystal clear. You basically get what you pay for.