NEW YORK — Fans of "Avatar" rave about how immersive it is, but it has a problem: The film only lasts 161 minutes.

If you really want immersive, travel to the amazing universe of BioWare's science-fiction epic "Mass Effect 2" (Electronic Arts, for the Xbox 360, $59.99). I've already spent about 50 hours there, and I can't wait to return. And there's no need for 3-D glasses.

"Mass Effect" introduced an intergalactic menace called the Reapers, an ornery bunch that wakes up every few millenniums and destroys all organic life. The main character, Shepard, managed to repel a Reaper attack against the headquarters of star-faring civilization, but as the dust settled, it was clear the battle was only beginning.

"ME2" begins with Shepard's death, although she's quickly resurrected by a shadowy group called Cerberus and its cryptic leader, the Illusive Man. (Shepard can be either male or female; I chose to play the game as a woman.) Cerberus awakens Shepard with the news that entire human colonies are vanishing, and provides her with a sparkly new spaceship to investigate the mystery.

Since most of Shepard's old crew don't know she's alive, she needs to assemble a new gang from a file of dubious resumes gathered by the Illusive Man. Most of them aren't the kind of creatures you'd want to be stuck with on a spaceship: a tattooed human psychopath; a stoic, fish-faced assassin; a bloodthirsty giant lizard.

Even the most incorrigible of them has a compelling back story, something developer BioWare has mastered over the years since its first blockbuster, 1998's "Baldur's Gate."