As I've now bought all of the Mirror Universe sets, I'm reviewing 3, 4, and 5 together here. 1 and 2 I reviewed recently and 6 I will review later.
3, 4 and 5 continue the line at its basic strengths, nice looking, cartoon-style superhero cut-out art cards. The good/bad alternates for each are as inspired as the first two volumes, though there is now greater variety I would say. The overall vibe is still very much a silver-age/bronze-age one which is fine for me but maybe not perfect for anyone hoping for more dark and gritty heroes/villains.
Ultimately these are a fine tool for use with any superhero campaign, especially as either quick heroes and villain inspiration, or simply as visual tools. Oh, and check the Inspired Device homepage for previews and freebies if you're undecided, or if you fancy a horde of faceless footsoldiers, heh.
[4 of 5 Stars!]