Um site muito bom que funciona como um motor de busca do Z-Library, Library Genesis e Sci-Hub é o Anna's Archive.

De acordo com o site:

We do not host any copyrighted materials here. We are a search engine, and as such only index metadata that is already publicly available. Books, papers, and so on can only be downloaded either through the original websites, through IPFS proxies (like IPFS.io), or directly from other people through torrents — we do not host such content on here ourselves. When downloading from these sources, we would suggest to check the laws in your jurisdiction with respect to what is allowed. We are not responsible for content hosted by others.

Ou seja, o site apenas indexa os links e metadados dos arquivos, fornecendo algumas opções de download.