Libgen, also known as Library Genesis, is a search engine for free books and articles. It indexes over 3 million documents from all over the internet, including many sites with pirated content. While Libgen is often used to find pirated copies of copyrighted books, it can also be used to find legal copies of public domain books and other free ebooks. To find free Libgen books, simply search for the title or author of the book you're looking for. You can also use advanced search options to narrow down your results. Once you've found a book you're interested in, click on the Download button to download it in PDF or EPUB format.