This was one of the earliest and most massive Russian ebook libraries. While the original site has changed forms many times, its database often feeds into modern mirrors and search engines used by the Libgen community. Current Working Search Links
rather than a direct host. It provides a searchable database that indexes metadata (titles, authors, ISBNs, and DOIs) and points users toward various "mirrors" where the actual files are stored.
Once you click a search result, you will see a list of "mirrors" (e.g., GET, Cloudflare, IPFS). If one link doesn't work, try the next one.