That is quite expensive! I've been reading the book and it is surprisingly contemporary, the storyline and the characters don't seem be from the 50s

Except for some old fashioned word choices it resembles a lot the modern ones, or perhaps it is the other way round
I agree, there aren't that many good new pony books around, they have become very commercial and some series are written so fast that all the books in it are far too similar. Some of my favorites from the Finnish writers are from the beginning of the 70s by Marvi Jalo, I still remember reading them over and over again. Was really pleased to find them in the flee market and rereading them after 20 years, still valid even for an adult! Good quality lasts!
Anne