Upon hearing of thy infamous Avengers film thus titled: Age Of Ultron. I thus thought about thy dear fellow; Ultron. It suddenly came to my attention that I know very little about thy fellow. My question to thee is what would thee recommend on such an occasion as to familiarise myself with thy Ultron?
I'd have to have a proper look through my collection for a good answer with issue numbers, so I'll get back to to you.
There was an interesting story where he evolved in such a way that he renamed himself Mark, and tried to reconnect with Hank. It was a nice change from him being evil all the time.
Definitely start off with the classic silver age origin stories. While Ultron first appeared in Avengers 54, he was known as the Crimson Cowl (mostly disguised.) Issue 55 is when he's first known as Ultron. Issues 57 and 58 really uncover his origin along with his creation of the Vision. He upgrades in issues 66-68, as well. (By becoming adamantium.)
Ultron Unlimited is my favorite. It is issues 0,19-22 of Avengers volume 3 written by Kurt Busiek and illustrated by George Perez. This story also has the history of Ultron in it so it is good for someone trying get familiar with the character.
Annihilation Conquest is a good story as well.
Unfortunately, I have not yet read some of the older Ultron stories.
I prefer Ultron Wars in the traditional comics series of Ultron. That was one bad ass Ultron in that series.
West Cost Avengers Vol 2 # 1 - 7 you have a very unique Ultron, who due to a glitch (Ultron 12) starts actually accepting humanity, hoping to put aside his childish feud make amends with his dad. That was a pretty good story.
Daredevil vol 1 # 275 and 276 has another very different Ultron story, where an Ultron, due to a glitch by Dr. Doom, actually falls in love.
Rest are very generic stories when it comes to Ultron. If you wanna know about Ultron i'd recommend you check these stories out.