After years of solo stories, post-credit appearances by Samuel L. Jackson and enough speculation to fuel a comic con’s worth of nerdgasms, The Avengers have finally assembled for a 3-D spectacle that brings together some of Marvel‘s greatest heroes in ways they’ve never been seen before. And the fact that this ensemble of superheroes is directed by Joss Whedon only amps the geekdom up that much more.

With the pieces all put in place over the past few years with The Incredible Hulk, both Iron Man movies, Thor and Captain America: The First Avenger, not much backstory is needed for The Avengers. Which leaves Whedon with the task of introducing the characters to each other and explaining how and why they have all come together. In steps Loki (Tom Hiddleston), the nemesis of Thor (Chris Hemsworth), to steal the powerful Tesseract, an extraterrestrial power source in the possession of S.H.I.E.L.D., the government agency directed by Nick Fury (Jackson), which forces Fury to launch the abandoned Avengers Initiative.

Realizing the fate of the entire planet is at stake, Tony Stark (Robert Downey, Jr.), Captain America (Chris Evans), Dr. Bruce Banner (this time played by Mark Ruffalo instead of Edward Norton) and Black Widow (Scarlett Johansson) agree to work together (reluctantly in most cases) in order to save the planet. Thor randomly shows up in a flash of lightning after they capture Loki, which leads to one of the film’s first big battle scenes as Iron Man, Captain America and Thor duke it out until they all realize their powers would be put to better use if they were combined rather than used against each other.

With Hawkeye (Jeremy Renner) and Erik Selvig (Stellan Skarsgård) under Loki’s control (not to mention that Loki is Thor’s adopted brother), the individual Avengers also have personal investments in this battle, which only adds to the suspense. Even though the story of a disagreeable group of heroes preventing the world from being taken over by alien forces is nothing new, Whedon is quite used to making otherwise tired concepts interesting again (remember what he did for vampires years before the Twilight craze and, more recently, for horror with The Cabin in the Woods?). And The Avengers has Whedon written all over it (quite literally, considering that he also co-wrote the script) with distinct egos, conflict amongst the team members and incredibly witty dialogue (he seems to have particular fun with the Captain’s wholesome anachronism, which makes sense considering Whedon’s best known for his clever stories about centuries-old vampires).

That being said, The Avengers also has a couple of the continuity flaws typical of most of Whedon’s previous works. For instance, it’s not clearly explained how Thor shows up, which is pretty important considering that the last time we saw him he was stuck on Asgard after the space bridge to Earth was destroyed. Nor is it explained why Banner’s Hulk goes from being an uncontrollable monster to being able to harness that rage (just when they need him the most, no less). But given the inevitability of additional sequels to all these movies, these are things that could easily be explained in subsequent Marvel Studios releases.

Until then, we’ll just have to be content with these heroes putting their differences aside long enough to stop the monsters attacking New York City through the portal Loki has opened from atop Stark’s skyscraper. Between the outstanding 3-D visuals (see it in IMAX if you can), the attention-grabbing dialogue, Alan Silvestri‘s bombastic score and just enough character development to keep the audience engaged, The Avengers is the big superhero team-up film comic book geeks and action movie fans alike have been waiting years to see. Now if only they can figure out a way to work Spider-Man into the next one (a post-credit scene proves there will be a next one, and another post-post-credit scene is added for an extra laugh), the universe will truly be a better place.

The Avengers. Directed by Joss Whedon. Starring Robert Downey Jr., Chris Evans, Mark Ruffalo, Chris Hemsworth, Scarlett Johansson, Jeremy Renner, Tom Hiddleston and Samuel L. Jackson. Rated PG-13. www.marvel.com/avengers_movie/.