Ok, here is my views on this TPB.
The story is quite nice, as Peter David has fun poking fun at both the Modern DC universe and the Sliver Age universe, but at the end he seems to favor the Sliver Age or at least that a new universe that combines both (like Alan Moore's Supreme) should be the new direction that comics should go. I agree with that statement. The artwork is really great as well, the artist Ed Benes seem to have been having maybe a little too much fun drawing the Supergirls
However, if you notice in the Modern DC Universe in this book every single women looks like a Supermodel, but this is not the case when we switch to the Sliver Age in the story. Also the men's muscles are much bigger in the Modern Universe than the Sliver Age version, so perhaps he was trying to say something about the change of taste and look of comics.
I would recommend it to any fan of the Sliver Age Supergirl!