Book lists are always the usual American,Anglo,Axis lists. Shame there isn't more available from Soviet,Japanese,Italian etc.
<S>...-Gixer
It's there, you just have to look a bit harder to find it. I suppose it has to do with wanting to actually sell some copies. The folks interested in the other stuff you mention are a much smaller group. You tend to find info on those birds in more general books.
There is a guy named George Mellinger who is from the Twin Cities that has always been a Soviet AF junkie. He's done some of the Osprey stuff on Soviet aces. I know he's done a lot of articles on them too.
There is a website out there that is nothing but Japanese WW2 Aviation.
It all comes down to how hard you want to look in the end, though I would agree it's harder to find the stuff you are interested in.