Does the world really need another X-Men movie? There have already been four in 11 years, and after a mediocre third installment — X-Men: The Last Stand — and an outright atrocious prequel, X-Men Origins: Wolverine, the answer would appear to be “no.”

But Hollywood is Hollywood, so a fifth installment, X-Men: First Class, arrives in theaters this week. While it’s not remarkable enough to feel like a necessary addition to the series, it does at least return to the “solid if forgettable” level of quality characteristic of the franchise’s two earliest (and best) entries.

First Class, a prequel (unrelated to Wolverine, thankfully), jumps from the present-day setting of the earlier films to the 1960s, when mutants (read: superheroes) were first appearing.

Professor X (James McAvoy, The Conspirator) is still a graduate student and hasn’t yet run into future nemesis Magneto (Michael Fassbender, Jane Eyre), who’s still Erik Lehnsherr, hunting down the Nazi who murdered his mother.

Said Nazi, played by Kevin Bacon (Elephant White), has adopted an American identity — taking the name Shaw and losing his ridiculous accent and mustache — and is apparently working for the Soviets.

This attracts the attention of the CIA, which recruits Professor X and Mystique (Jennifer Lawrence, The Beaver) to help stop Shaw. In their efforts to do so, they run into Magneto and begin assembling a team of several other mutants, leading to the eventual creation of the X-Men.

Movie No. 5 is about the time when any franchise gets a reboot, but while First Class does ditch the entire cast of the earlier movies (save one cameo) and shifts the timeframe by 50 years, it doesn’t feel like much of a departure from the earlier films.

In particular, the tone and themes go virtually unchanged. The series has always operated on a continuum that runs between “relatively nuanced Civil Rights allegory” and “complete, utter nonsense,” and First Class is no exception.

One scene may offer a fairly subtle look at how difficult it is to not hate an oppressor, while in the next a blue-furred wolf-man will beat up a Lucifer look-alike with teleportation abilities while on the deck of a battleship during the Cuban Missile Crisis. It can be a bit uneven, to say the least, but it also lends a trace of meaning to all the superhero melees.

The budding friendship between Professor X and Magneto — and its inevitable dissolution — is, wisely, the film’s focus. The two have always been the series’ most well-drawn characters. It’s easy to sympathize with would-be villain Magneto, and even saintly Professor X is given a few realistic flaws and blind spots, especially in his relationship with Mystique.

McAvoy and Fassbender both do a solid job taking characters previously played by Patrick Stewart and Ian McKellen, respectively, and making them their own.

McAvoy, for example, is far more suave than the erudite Stewart. It’s hard to imagine Stewart pounding back beers and flirting with coeds the way McAvoy does, but rather than feeling like an entirely different person, the Professor X of First Class just seems like a younger, brasher version of the same character.

At the same time, Fassbender (who, between this and Jane Eyre, is having an excellent year playing sympathetic sort-of-villains) nicely captures the anger and cynicism McKellen brought to the role, giving the eventual antagonist the weight and depth it calls for.

It’s beyond that core relationship where the film falters. The younger mutants who make up the titular first class of X-Men all feel generic and aren’t as important to the future story, making them difficult to care about. What’s more, there have already been so many mutants in the series that the writers really seem to be scraping the bottom of the barrel, with such lame heroes as “guy who can scream really loud” and “guy who has hands for feet.”

Still, there’s more here to like than not. Beyond McAvoy, Fassbender and the occasional moment of thematic subtlety, there’s plenty of the requisite superhero theatrics, which, as executed by director Matthew Vaughan (Kick-Ass), are entertaining if uninspired. The fight scenes may not be very original, but they’re still full of the kind of chaotic spectacle you hope for in a CGI-fest.

The same can be said of the film as a whole. There’s very little that’s unique or arresting about it, but you can do a whole lot worse in terms of disposable summer entertainment.

RATING: 3 stars out of 5

diversions@umdbk.com