The Avengers are one of earth's mightiest supergroups, formed of heroes as diverse as the Hulk and Captain America. In their long history, they have gone through many lineup changes and fought and made many enemies and allies. This book collects all the information on their members, villains and allies into one place.
This is a very thick book, as the number of heroes and villains who have appeared in the pages of the Avengers is immense. There is even crossover with other members of the Marvel Universe, as Wolverine has recently joined the team after being part of the X-Men. Each Hero and villain is given their backstory, real name, and how they became part of the Avengers or ended up fighting them.
The villains run the gamut from Norse Gods like Loki to recent foes like Veranke, the Skrull Queen, and Foes turned friends like Demolition Man. In fact, most of the heroes and villains in the Marvel Universe come from either the Avengers or the X-Men, which are two of the largest groups of comics in Marvel. Some villains, like Magneto, have fought with both, either through their connection to a member of the Avengers (like Beast and Wolverine), or just from being in the wrong place.
This is a pretty sizable collection of heroes and villains, and if you already have past versions of character guides, this one might provide you with an update on what your favorite hero or villain is doing now. But it's a lot of information in one place. It's probably more useful to someone wanting to run a Marvel Heroes game or for someone who is planning to see the Avengers movie when it comes out and wants to understand the history of the group.
Yes, the Hulk was part of the original Avengers group- for a whole two issues. His "Hulk Smash" way of doing things once he had changed from Bruce Banner didn't fit in too well with the rest of the group. While I wonder how the upcoming movie is going to handle that (will they turn Bruce into a villain, like they did in the Ultimate Avnengers movie, or will they just allow him to leave, like they did in the comics?). In any case, this book provides a very good background on the heroes and villains, but aside from giving details of the battles they fought with the villains, it's more to help you with the details of who a particular hero is than the actual battles they have fought, especially if they clashed more than once.
Buy this if you want to know more about the characters in the upcoming Avengers movie and understand some of the history of the comics. For the actual stories and battles, it would be better if you actually read the comics back-issues. Recommended.