Ultimate Iron Man I and II are not 1610 (Ultimate) Anthony Stark's definitive origin story. It was revealed in Ultimate Comics: Ultimate Avengers vs New Ultimates that these two miniseries depict a comic version of a Japanese anime about Tony's early life. This isn't the true origin story of Iron Man.
Ultimate Iron Man I is a five issue miniseries written by Orson Scott Card with art by Andy Kubert.
There is a heavy focus on sci-fi elements from Card, which gives this book less of a Marvel “feel.” Which isn't exactly a bad thing. Card weaves together a fantastic and intelligent origin story. It's a shame that all his hard work was retconned to be nothing more than a fantastical tale. Kubert's art is excellent. Attention to body language, settings, and background are astonishing. The miniseries starts out by revealing the accident that gave Tony Stark such a genius mind. It should be noted that the first two issues focus heavily on Howard Stark, Tony's father. Ultimate Iron Man I includes extreme sci-fi and political elements. Such as Tony's physiology being altered in his mother's womb or Zebediah Stane making a play to wrest control of Stark's company from him. Readers not familiar with these types of subplots might be turned off by this. I personally loved it and felt it added a unique depth to Tony that I honestly didn't expect from this miniseries. We'll see Ultimate versions of Obidiah Stane and Jim Rhodes introduced and the final issue ends in a cliffhanger that leads into the sequel miniseries.
Ultimate Iron Man II is again written by Orson Scott Card with a different artist, Pasqual Ferry. Ferry's art isn't bad, but it doesn't come off as good either. Sometimes characters heads are too big for their bodies and vice versa. The first issue is great and then seems to spiral downward in quality. It felt like Card was losing interest in this project, and started putting less effort into his work. This second miniseries is almost purely political and action. The story felt extremely rushed, ending in a disappointing conclusion. The plot of this series is Tony Stark being manipulated by a mysterious, menacing government agency into using his super-tech in their gruesome fight against Middle Eastern terrorism. While this creates a miniseries more centred around Iron Man in action, I couldn't help but ask myself, “If Tony Stark is a genius, why couldn't he tell he was being manipulated?” This second miniseries is step down from Card's excellent first entry, it is still worth checking out.
Overall, these two miniseries may be out of canon, but it is still a fun read any comic lover can appreciate.