Osprey Aircraft of the Aces #58: Slovakian and Bulgarian Aces of World War 2.
I have to say that these are appearing more and more esoteric. I'm not really enjoying the books so much as others by Osprey, and I suspect that I'll be flushing the lot rather than going on reading them. This one deals with more pilots from another German ally in the war. I just wasn't all that interested.