They definitely exist.

I don’t have links because I’m on a tablet and won’t be booting up the PC I use for that today (expected power surges) or maybe even tomorrow. But they definitely are out there.

Soulseek tends to be more reliable for books in terms of easy to find publicly. Usenet is usually the default book source, but collections like you want are probably going to be easiest to find via soulseek.

Classics though, you can just get them from project Gutenberg, if they’re public domain, and the real classics tend to be. That’s where damn near my entire classics folder came from.