Tony Stark was actually introduced to the world in the pages of 1963's Tales of Suspense #39, in an origin tale that was faithfully retold in the first film: injured by a booby trap, he is kidnaped by terrorists and forced to make weapons, eventually breaking out in a big, clunky and destructive piece of robotic armour. It's a fun, short tale, but maybe not the best for modern eyes. Chief Marvel architect Stan Lee (who co-created basically every big character) has a writing style that hasn't aged well, unless you bloody love alliteration, and his original intentions with the character - to troll Cold War-hating hippies by making a rich arms manufacturer a superhero - leave a nasty taste in the mouth. It's also incredibly short, just a single story that doesn't even take up the entirety of the issue it was published in. For a richer, fuller and more nuanced take on Tony Stark's origin and his early adventures as Iron Man, you could do a lot worse than picking up Kurt Busiek's Iron Age stories. Essentially Iron Man's Year One, the Iron Age retells the start of Stark's superhero career in a style more palatable to modern audiences. Not to be confused with the recent time-travelling crossover event of the same name, the Iron Age is a rollicking good read that takes elements from Tales of Suspense and the early Iron Man comics and spins them into a consistent, engaging story, introducing the core supporting cast (Pepper Potts, Happy, etc) as well as hinting at some of the future problems facing Tony Stark in both his professional and private lives. If you want a refresher on the back story and how it differs in the comics, this is the place to start.
Tom Baker is the Comics Editor at WhatCulture! He's heard all the Doctor Who jokes, but not many about Randall and Hopkirk. He also blogs at http://communibearsilostate.wordpress.com/