Honest question - what examples are there of literature that can only be obtained on the dark web? Perhaps I'm closeted but I'm unaware of such books. For exam

Honest question - what examples are there of literature that can only be obtained on the dark web? Perhaps I'm closeted but I'm unaware of such books. For example right now I'm reading a sci-fi book that remains unpublished in Russia, but it's available in the west. Or the other day had a browse of "steal this book". Genuinely curious.