If you’re the “trash” person (as I am) for not seeing Age of Ultron or any Avengers movie like “others” have called you, I got something for ya. Now don’t get me wrong, I love comics, I really do, but there are tomes of them that I can’t keep up. And since I like to start at the beginning and details, I can’t read volume 83 or watch a movie unless I have the beginning. So to help out with that I discovered: http://www.marvelousdb.com.
Its a database that has information on every marvel character ever created from 1950-present.
You can search by universe, comic, gender,color, etc and it will tell you all types of cool and sometimes asinine shit like: height, weight, education, family history, powers and the list keeps going and going. Also if you want that comic, just click on it and it will take you to an external site where you can buy hard or digital copies of it.
So there you have it. Find out all the background stories of all the marvel world. Then go watch the movie or start in the middle.