Bing often indexes directories that Google has removed due to DMCA requests. Try: intitle:"index of" "pdf books" on Bing. DuckDuckGo (using !g bang) is less effective but respects privacy.
: Excellent for finding academic PDF versions of papers and scholarly books. Open Library intitle index of pdf books
[ICO] Name Last modified Size [DIR] Parent Directory [DIR] fiction/ 2024-01-10 - [ ] alice_in_wonderland.pdf 2023-12-01 1.2M [ ] dune.pdf 2024-02-15 3.4M Bing often indexes directories that Google has removed