I just discovered that I'd read Dhyani Ywahoo's Voices Of Our Ancestors back in 1988, right after it came out! I knew there was "something about it", but I'd assumed in recent years that it had some vibe about it because it was a gift book that I was feeling guilty about not having read ... instead now I suspect that the "thing about it" was that it was a duplicate copy of something that was already on the shelf (with my library seal impressed in it) and that since it had a note from my friend, neither copy was really "recyclable", thereby creating a "unique status" for that book. Dang.
Needless to say, this "shock" came as I was unloading books from another shelf to log them in ... sort of a "how did this get here?" moment. Fortunately, I recently discovered a print-out from my previous attempt at cataloging my collection (which, while having less detail than the current LibraryThing catalog, at least tells me what year stuff was read) a dozen years or so back, and I was able to at least give it some context.
Interesting that I made it through that whole book without having a flash of "oh, I've read this before!" ... how bizarre.