The sketches are a bit variable but the base set and inserts are excellent. They are mostly covers and artwork from the comic so there's a fair bit of Alex Ross artwork and several others. In addition, some of the sketch card artists are artists from the comic.
As a comic collector, I also have read the comic (though not the spinoffs). It's quite good and has excellent art, but there's way too many characters so it's very hard to work out what's going on.