My oldest book dates to the 18th century. It’s not my most valuable book (I’m not sure which is, but my guess would be the signed limited edition of Graham Greene’s Monsignor Quixote would be it).
I keep the valuable books on a special shelf so that after I die, my kids will know that those books should probably not be sent to the library book sale.
I grew up with a Readers Digest atlas¹ which had reproductions of antique maps on its endpapers. Aside from weird distortions of the shapes of continents, it also had Australia as a peninsula extending from Antarctica. I spent a lot of time studying that old map.
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1. Speaking of old maps, this atlas had such details as Pakistan and Bangladesh as a single country, Vietnam as two countries, and an extensive section on the then-new concept of plate-tectonics including maps showing prehistoric configurations of the continents.
I keep the valuable books on a special shelf so that after I die, my kids will know that those books should probably not be sent to the library book sale.