You mentioned Folio; I’m a big fan. I really do find that the quality is worth the price, and they’re meant to be heirloom books, so I pick up 2-3 a year that are extra special to me in some way (mostly children’s works; those Folio books are so alluring with their illustrations, I want my kid’s grubby hands all over them, reeling her in with the delight of reading…). Other presses with editions you might enjoy are Juniper and Eaton.

But some more tips: there are Instagram accounts you can follow for truly rare or limited editions. Very few Folios are “rare” - they’re just expensive, and that makes them cost prohibitive. @The.vintage.library is great for inspiration; she often focuses on specific volumes or collections. If you’ve got deep pockets, @sotherans_piccadilly is “one of the world’s oldest antiquarian bookshops,” and they’ll post some truly RARE works from time to time.

Lastly: eBay, of course. Although not valuable, there are quite a few paperbacks we have from the 60s and 70s, during the golden age of cover illustration. We’re pretty particular about the editions of books we want, and every so often, we get lucky on there.