Warren Ellis' work is always fun to read and this short 4 issue run on two of Marvel's best loved heroes is no exception. The title says it all - Iron Man fights Hulk after a failed experiment to infect Banner/Hulk's blood with nanotech to control the Hulk genes. However the fight is short lived as another failed experiment - "the Leader" (a guy with a big head) - tries to take the blood of both Iron Man and Hulk and an entire issue is devoted to Leader's origin (very dull) followed by a swift and unsatisfying conclusion.
The entire book is really a bridge between Mark Millar's books "The Ultimates Vol 1" and "Vol 2" where in Vol 1 Hulk goes on a rampage in Manhattan killing 300 people and Vol 2 where he is imprisoned, facing trial and a surefire death sentence. If you've read Millar's run you'll know how that pans out and I highly recommend those books over this weak place holder.
The artwork in the book is also really poor, looking at it feels like I'm looking at art through a window with water pouring down it, it's very unpleasant. While I like Ellis, this is one of his weaker efforts. If you're looking for a better Warren Ellis/Marvel book I suggest "Armour Wars". "Ultimate Human" is definitely only for the fans.