z-lib is one of the most popular platforms for free books, and its collection is impressive. Most of the books are in good quality, but sometimes you’ll come across poorly scanned PDFs or ePubs with formatting errors. It really depends on the source of the file. The search and download process is simple, though, and you can often find rare or hard-to-get books. If formatting is a big concern, other platforms like Project Gutenberg offer well-structured books, but their selection is more limited.