There was a series of adventure and science fiction books by foreign authors (think Alexandre Dumas, Jules Verne H. R. Haggard, Mark Twain, but also a number of Russian & Soviet adventure & SF authors - full list
here for anyone interested; in Estonian but author names should be clear enough) published here in 1955-1962, fifty five books in total.
We had a number of them when I was a child, thanks to my grandma having bought them when she was young and my mother was little - but most of the ones we once had fell victim to water damage (flooding caused by bad plumbing) when I was a baby, so we only actually had maybe a quarter of them left; the rest I had to get from the library to read.
Once they finally started showing up in used books shops in early 1990s, and I had my own income, I embarked on a project to collect the entire series. It took me quite a few years, as some books were considerably rarer than others (huge differences in print numbers) and some ended up costing me what was at the time a small fortune, but I have the entire series now and it's really one of my most cherished possessions as far as books go.
Out of newer books, I'm increasingly pleased with my growing collection of Skulduggery Pleasant books by Derek Landy - in particular with having managed to acquire both the US and the UK uncorrected proof copies / ARCs of the first book. I've also got them both signed, in person, to me, with some extra doodles in the UK proof copy. (Additionally, as a person fairly active in that fandom, I was fortunate enough to get a completely unexpected cameo appearance in the latest book - and got one copy signed to me by my character name, which, well, makes that particular copy one I do cherish.
)
The oldest book I have is ... well, I'm sort of in two minds about whether to count it as a cherished paper book or not, as it's a copy of the Bible, printed in 1903, left to us by my great grand aunt - so as a "family heirloom" thing, it's rather cool; on the other hand, I don't think we've ever had a religious person in our family (including said great grand aunt and her family) so there's no particular emotional significance attached to it other than being passed on through several generations. As an object, though, it looks quite awesome, with its Gothic script and yellowed pages.