My title is a bit of a misnomer. Gantz from volume 1-15 has been very well-written and drawn, if a bit exploitative. Throughout you're often overwhelmed with drama and there is rarely a moment that isn't filled with tension. But what's damaged Gantz is it's fondness for showing extreme, often needless, images of violence, and the artists penchant for displaying large breasted women naked, again needlessly. For me, this is a plus as I tend to enjoy darker, more adult manga (like Berserk and Monster) but I can see why people would look in a different direction when reading Gantz.
(I'm going to keep this spoiler-free so please forgive the cryptic description ahead.)
Volume 16 of this series, however, takes such a dramatically different turn that my hope for the future of this story has grown. Many who have read the series probably got into the same mode I have, which is kind of a settling. It started to feel like the story was getting into a rutt. Kei goes to the room, meets new people, convinces them that they're going to die, and then they go kill aliens. Between that we see Kei attempting to interact in the normal world knowing what he knows. Along the way we get to meet future players in the Gantz game, and get a chance to get to know them a little, though often never enough to care when/if they die. Oh, and don't forget nudity, blood, and strong sexual situations.
Gantz 16, however, infuses a lot of the scenes in this volume with heart and true human emotion (some has been building in previous volumes). This allows for the reader to care far more for the characters of this story. Kei, who has been the hero throughout, faces some of the most troubling times he's ever faced, far beyond anything he's faced thus far. And the surprising ending of this volume is enough to make a grown man shed a tear. Without spoiling, it leaves an impression, and I genuinely can't wait to read the next volume to see what happens. Also, a new twist to the Gantz world is revealed, one that has me curious to see where it can lead.
There really isn't much in the way of recommedations. If you read this far, you're going to continue reading I'm sure. I just hope that people get the same impact from this volume that I had. It really is the best volume of the bunch and it makes me hunger for the rest of the series.