Same situation in Romania, some of the best math problem books I found were a bunch of books printed before 1980's. The problems were just wonderful. I was desperately searching for them for my kids through my father's library.

In 1990's after the revolution we got humanitarian aid from Western Europe, including some French math textbooks. They were so low level (simple) I was in disbelief. Useless.

I had the same reaction in Poland, when my grandfather gave me some textbooks from his collection. They were an order of magnitude better than what I was using at school.

and, somehow, the economic and social system in France is much better than the one in Romania

my take is that the western-style school focuses on getting students life skills, while the eastern-Europe one focuses on cramming knowledge in the brain

Maybe it's also the context, the gradual buildup France had over Romania at the time and now. Romania endured the communist regime for many decades and was very much isolated.

Can you please share some books you enjoyed?

The ones I spent most time with were volumes titled (translated) "Selected problems in higher mathematics." I worked out of a German translation for one volume while I learned a smattering of Russian and then the Russian for a second one. This was to fill in assumed background in things like integration that was assumed by Landau & Lifshitz.

It's been long enough where I have no idea of the author.

What subjects are you after?

Also, the enjoyment was not supposed to be from reading the book, it was from passing the exam.

Not OP, if you know any great English translated Linear Algebra title or statistics.

Unfortunately the ones I know were not translated.