This was a gloriously fantastic idea, and at the best of times, the huge size is magnificent for showcasing the art. That being said, the stories and art are incredibly inconsistent. The best stories, like Metamorpho, Flash, the Demon, and Supergirl, all have a significant hook--particularly the Supergirl story, which is hilarious, and the Flash, which is like some awesome episode of Twilight Zone. The Superman and Wonder Woman stories both have incredible art, but neither one has a particularly amazing story. But too many of these stories or just passable--Green Lantern, Hawkman, Strange Adventures, Kamandi, Metal Men, and even Batman all look good in the big size, but the story isn't big or interesting enough to really warrant any real attention. And one of them--the Teen Titans story--is awful in every way: the story is a muddle with too many characters, and too much tie-in to the "real" comics world, and the art looks like a cartoon--which might be good, except the palette is so bland it makes you want to take a nap instead of reading it. Overall, a cool idea, but the writers (and a few of the artists) didn't really live up to the over-sized expectations.
(Also, (and I didn't think I'd ever say this,) this book is too big. It's ungainly to read, and I dropped it a few times trying to prop it up in some way. But that's sort of inherent in the idea, I guess.)