Yeah, I know, books maybe have gone out of fashion and are a bit old and all but I still think that books are good and really helpful when you need more reliable information on a certain topic such as the Avengers.
At good way to find out useful information about the heroes of this mighty team (and also the evil masterminds behind these desperate attacks) is The Marvel Avengers Character Encyclopedia which is a detailed book covering all the 200 characters affiliates of the Avengers, a great read for any beginning comic book fan (or better yet Marvel fan!). Probably the best place to get this book is Whsmith because it’s really cheap and also you get free delivery if you buy over £15 but the last time I went on, it was out of stock. I think the next best place is Amazon.com but it is quite a bit more expensive.
A book, which I have, is The Avengers The Ultimate Guide to Earth’s Mightiest Heroes! This book covers a lot of this might team, it is a slightly bit childish but it has a lot of useful information on not just the team and villains but also on some great comics about this team. The two cheapest places to get it are Amazon.com and also Waterstones.com which they both provide free delivery (but sadly only in the UK which is a bit bad for the international fans) which is a good reason to buy from them.