I'm actually not a big reader of comics or graphic novels, but there were two words on the cover that sold me: "X-Men" and "Whedon". If you like either or both of those things, you'll like this.
In some ways this was my introduction to graphic novels. I'd read Archie comics as a kid, and that was about it. If you're not really a graphic-novel reader, but you do like fantasy, this is a great place to start. Whedon's non-sequitors are slightly more jarring in comic book format (probably because the characters expressions are frozen in that moment, rather than showing the slight eye-roll or blink that would convey everything in an instant), and you can certainly tell he usually writes for TV, but in general I was able to figure out the conventions (such as flashbacks, internal monologue, and cutting) while still being wrapped up in the story. And of course the Whedon-esque dialogue is like a drink of cool water to a fan. It doesn't disappoint. This is a very funny book as well as being an adventure fantasy story.
The artwork is beautiful (with the strange exception of the cover, which looks anatomically odd in places). It's in full colour and beautifully realised detail. The characters are instantly recognisable and (other than Kitty, who seems much older in the first scene than the rest) consistently drawn.
Whedon has always loved the character of Kitty Pryde, who tends to divide fans. This book focuses on her, but as a newbie to her character I liked her - especially the friction between her and Emma. If you have a hatred of cuteness, however, her sweet awkwardness is likely to rankle rather than charm.
Originally published as Astonishing X-Men #1-6.