If you've never read "The Girl With the Dragon Tattoo" and only seen the movie, you may be missing out.

I certainly was, until DC Comics began adapting Stieg Larsson's popular thriller into graphic-novel form (in two parts). And I still remained shrouded in ignorance of the full impact of the novel after reading "TGWTDT Volume 1," which offered little more in the way of information than I gleaned from the movie screen.

Then along came "Volume 2."

Remember when Mikael Blomkvist (the reporter played by Daniel Craig) drops in on Lisbeth Salander (the girl of the title, played by Rooney Mara) and her one-night stand? In the graphic novel, she's no pickup — she's Lisbeth's girlfriend.

Remember when Blomkvist broke up with his editor/girlfriend Erika — temporarily, as it turned out — so that he could sleep with Salander with a clear conscience? In the book, both characters are still in relationships when they sleep together, and it doesn't appear to matter to anyone involved.

That goes double for Blomkvist, who is not only sleeping with Salander while still in a relationship with Erika (who is married to someone else, by the way), but is also having an affair with Cecilia Vanger, niece of Henrik Vanger, who hired Blomkvist to solve the murder mystery. That's three girls at once, and none of them cares that he's sleeping with the others. Some of them even have tea together. It's significant that Salander has a girlfriend in the book, because she dumps Blomkvist to go back to her.

Not all of the revelations are sex-related, though. In the movie, the truth about serial killer Martin Vanger is revealed to authorities after Salander rescues Blomkvist. But in the book, Salander leaves the wounded Blomkvist at his cabin ("Don't go!" he whimpers. "Please don't leave me here!") to go burn down the killer's house, including all his videotapes, files and photos.

She burns the tapes, she says, to keep them from leaking to the Internet as snuff films and pornography. She feels they would victimize the victims a second time, make Vanger a hero in certain sick quarters and "give the next generation of killers materials … ideas … aspirations … goals."

Instead of revealing Vanger's guilt, Salander blackmails the Vanger Corp. into compensating all the victims' families, and donating $2 million annually to Swedish crisis centers for women and girls. She doesn't get mad, apparently — she gets even.

Leaving out how Salander deals with the serial killer's legacy was a disservice to the material — and the audience. It's of a piece with Salander's revenge on her rapist, and how she deals with the corporation that framed Blomkvist.

It demonstrates why she is — in her own weird, damaged, anti-social way — a hero. It's Salander's gender that throws us off, but once we poke through our own preconceptions, we realize that she's the heroic loner who swings in the window to save the day, and it's Blomkvist who's the damsel in distress (and sex object). "Girl" is mostly a standard adventure story, but with a spicy gender reversal that continually confounds our expectations.