He's Tony Stark, a cool exec with a heart of steel. He's a founding Avenger, often called the Golden Avenger. He debuted in Tales of Suspense 39, cover-dated March 1963. Today he's arguably considered an A-lister, largely thanks to the trilogy of Iron Man movies starring Robert Downey Junior, as well as being a major part of the two Avengers movies (Avengers 2: Age of Ultron in theatres now - shameless plugs dept.). In the comics themselves, he may not have been the biggest star, but he's consistently been a cornerstone of the Marvel Universe for decades.
This reading project will cover the Iron Man stories featured in Tales of Suspense 39-99.
It was rather amazing how fast KIrby could draw a story, and usually very well, although IMO his artwork looked much better in the mid-60s when the number of pages he was drawing each month was reduced. His style did take a turn for the craggier during his last year with Marvel.
I think the movement of Kirby's art in that direction may have been played down for a period by the inkers, to the art's benefit. Joe Sinnott supplied a slick finish; Vince Colletta Colletta-ised his shadows and eliminated some of his squiggles; Frank Giacoia prettified the art (and Don Heck's when he inked The Avengers); Syd Shores imposed a Syd Shores look. Contrast the issues of Thor inked by Bill Everett (mostly from that final year).