Historic importance mixed with solid writing
I've been a big X-Men fan since I was a kid, having been totally in love with the animated series. In going back and finally reading the old comic books, although I love Beast, I had trouble getting really into the early stuff. Compounding the fact that the other four members of the original team have never been among my favorites, the dialogue was always really rough. I am definitely a modernist when it comes to comic books; I feel less is more in terms of dialogue for the most part.
"Giant Size X-Men #1" is really when X-Men becomes more of what I know and love. Colossus, Wolverine, Nightcrawler, and Banshee are all some really great characters, and although I'm not a huge Storm fan, I definitely prefer her to Jean Grey. It is pretty astonishing the number of influential characters that all debuted in this single book, and that is why it is such a landmark.
The story itself is very good. Len Wein does a very good job of introducing all of the new team members, giving just enough information about them without being too heavily drenched in back story and other information that would take away from giving these characters an opportunity to have a first adventure together. The dialogue is also a significant upgrade from the earlier era of X-Men.
The biggest fault of the book is the character Thunderbird. Wein unfortunately relies too heavily on stereotypes of Native Americans, even making the character make off-hand references to Little Big Horn. It's kind of a shame that racism was still a problem in comic books at this point, but at least there can be some comfort taken in that Storm isn't written badly. Luckily, Thunderbird would end up going away rather quickly.
The art of this book is solid, and aside from the bonus stories at the end (which are pretty much throwaway and not worth the pages) this is an above average story that gets to be special because of its lasting influence on the series. If this book had never been written, there's no telling what X-Men would be like now. It is definitely a must read for any comic book fan.