These are stories that created the foundation for the Marvel Universe, and much of modern comics in general. This is the foundation for both the style of writing and art of superhero comics for over forty years now. Not only that, they're just good superhero stories.
Of course, if you're considering buying this, you probably already know that. Not many people are going to plunk down $70 for this collection if they're not serious fans of comics and the Fantastic Four. But if you are a serious fan, this is well worth the money.
The first thirty issues of the FF, plus the first annual, on archival quality paper, oversized and hardbound. And with extras! To be fair, many of the extras are reprints of Stan Lee's introductions to the Marvel Masterworks volumes, but there's more extras than that. Perhaps most interesting to me is that the original letters pages are reprinted (though, sadly, not reprodused at the quality the rest of the books are.) Its kind of amusing to see letters from then-young fans who went on to be major names in the comics industry, like Roy Thomas and the late Mark Gruenwald.
Flaws? Well, this does not represent the absolute best of the Lee-Kirby Fantastic Four. That comes in the (hopefully) second omnibus volume, when, in about a dozen issues, we get the the Black Panther, the Inhumans, Galactus, the Silver Surfer, and the classic tale of heroic sacrifice, "This Man, This Monster" from issue #51. But there are still great stories.
The art, to be fair, looks a little crude by modern standards. Remember, though, that Kirby was drawing several books a month -- he just didn't have the time modern artists have. Nor did he have high-end coloring techniques. His style was what revolutionized the industry. Yes, it had its quirks (square fingernails, for instance), but Kirby revolutionized how comics are drawn.
The stories, too, seem a little crude by modern standards. There's not a heck of a lot of continuity between issues -- certainly not by the modern standards of multi-issue, multi-title epics. But there's a lot here that had never been seen before -- characters who really seemed human, despite having super-powers, rather than the almost-perfect paragons of virtue that were the standards up until that time. They argued with each other. They had financial troubles. One of them didn't even want to be a superhero.
This is not a volume for a casual purchase. However, any serious comics fan should acquire one.