Win32 isn't a type of assembly. Assembly is all based on the processor. 80x86 ( x86 ) is Intel syntax, 68000 is Motorola, ARM.. there's alot. The difference isn't really that big, but, for a language like assembly, changing syntax is difficult.. I've only just reached comfort zone with writing assembly programs.
I think you should stick with x86 though, 'cause it's badass. |:
Also, sorry, I can't recommend anything good, I just downloaded a crap load of different books until I found a good one...