Ironically, back in those weird days when half of Europe was stuck under the Communist rule, math books like that were printed in ridiculous amounts (hundreds of thousands copies). Sometimes you couldn't buy the most basic things, but you could always get a good book about math for roughly the same money you would pay for a loaf of bread.

Thankfully those times are long over, but many of those books can be purchased today for next to nothing (often for sums like 50 CZK, which is something like $ 2), because everybody hates math and everybody hates Russian. And those books have been serving me really well for years.