Production of this miniseries had a rocky start. Originally intended as an alternate universe tale where a mainstream timeline character would be trapped in a place where the faces are the same but the people behind them are different, that idea was completely derailed by the "Mutant X" series with the same premise. With deadlines pressing, Busiek and Pacheco drew up a different idea but didn't have the time to plan it all out. Instead, they set up a series of signposts and filled in the blanks on the way. It had certainly worked for creative teams on "Avengers" in the past, as Roy Thomas and Neal Adams did the exact same thing with "The Kree-Skrull War."
So, here's the what they came up with: Rick Jones is ill, and the first Busiek-era Avengers team takes him to the Kree Supreme Intelligence being held in captivity on the moon in an attempt to save his life. Once they leave, the time guardian Immortus arrives to kill Jones, afraid that his previously-manifested "Destiny Force" godlike powers will lead to humanity conquering and oppressing the universe. Arriving to stop Immortus is Kang... who eventually is supposed to evolve into Immortus. As Kang finds himself on the losing end of the battle, a revived Rick is prompted by the Intelligence and Zodiak-member Libra to call on a team of Avengers. Summoned is a squad made up of members from the past, present and future: Captain America, Hawkeye and Yellowjacket from the "then," Giant Man and Wasp from the "now" and Songbird and Genis-Vell from (possible) days yet to come.
Now, if you're unfamiliar with what the hell I'm talking about, that's OK: it means that you understandably haven't read hundreds of Avengers comics. Hell, when I first read this, I hadn't either. But herein lies the brilliance of "Avengers Forever:" in a world where people are so eager to reboot, this is a celebration of everything that had happened to the team. Everything. If you don't know about something, you learn about it here and think "cool." This is lost on so many companies now who make the crass mistake of tossing aside history periodically, underestimating the intelligence of their audience. If something great happened, there's no harm in telling people about it and letting them enjoy it.
Let's get back to Rick's team. While he's chosen some big names, they are not quite at the height of their abilities. Cap has been ripped from just before he became Nomad and has lost faith in his country. Hawkeye has just just been stripped of his size-changing Goliath powers and has no trick arrows. Yellowjacket is plucked from the middle of a two-issue arc under Roy Thomas where Hank Pym had lost his mind and become the opposite of himself. The additions of Hank as Giant Man in present-day along with his ex-wife Wasp (who was Yellowjacket's fiancee in his era) complicates things. Songbird, meanwhile, was a half-villain at the time and couldn't be trusted and the same could be said for Genis-Vell, who is clearly hiding a secret.
So, the team has to hop through history to find Immortus, they come across other incarnations of the Avengers, team up with Kang and I really don't want to say anything more and spoil the rest of the plot. Let's just say that the climax has an endless number of Avengers fighting another endless number of Avengers and if that doesn't make you want to buy this, I don't know what will.
Busiek and Stern really go the extra mile here when it comes to continuity, not just highlighting some of the big moments of the Avengers' past, but also giving a nod to some things that happened outside the timestream. Example? Lex freakin' Luthor cameos in a panel. Bigger than that, the writers take the reality-bending opportunity to fix major continuity issues from the past, such as the construction of The Vision from the parts of the original Human Torch. An entire issue is devoted to patching up holes, and it's gripping. An additional issue mends Kang's complicated continuity and it's equally mind-bending. I have no idea how the creative team managed to remember all his life's events to begin with, let along organize them.
On top of this, Pacheco is adding easter eggs throughout the course of the collection, as helpfully highlighted by an index. An alternate version of Rick Jones has... well... quite the costume. Every rag on it has history. How crazy do Pacheco's easter eggs get? Let's just say you should keep an eye out to see if you can spot a certain "Man of Steel" and a certain "Caped Crusader" among the warring Avengers.
In short, this is the massive epic with an uncanny attention to detail that all geeks dream of in any property. I would argue that there is no other work anywhere - ANYWHERE - in Sci-Fi or Fantasy that pulls it off to this level. This is a marvel, diction intended, and the more Avengers you read, the better it gets.