If you are looking specifically for books in , these sites are highly recommended:
: Focus on "Public Domain" works (usually books published before 1928) or Creative Commons licenses.
: A search engine for PDF files that allows you to preview and download millions of documents. 🇷🇺 Popular Russian-Language Resources
: While primarily a social network for readers, it often links to free legal versions of books.
: A massive digital archive of Russian periodicals and books. 📱 Tools for Reading PDFs