His name is John. He’s a boxer, a drug addict and a Vietnam Vet.

Her name is Caroline. She’s a poor white trash girl living a dead-end life.

The two meet at a state fair, fall in love and run off together in search of a happier life. Then they get stuck in a dark gambling town. Then John has a drug relapse. Then their relationship falls apart. And the story just goes downhillfrom there.

Downhill is a familiar direction for Aimee Mann. Often cited as one of the finest songwriters of her generation, Mann has a knack for picking her way into the middle of a tragic story and finding the little bulb of humanity that makes it tick. Her new concept album, The Forgotten Arm, which details the adventures of John and Caroline in a dozen technicolor tracks, is no exception.

“I’m more into the in-depth profile than the short vignette,” Mann says with a wink from her studio in California. She sounds animated, a little mischievous, and overall nothing like the gloomy girl she’s made out to be. In fact, for someone who’s given nicknames like “Ms. Misery,” Mann sounds downright chipper.

“Truly, most of my friends are comedians who think I’m kind of funny. I mean, somebody of my circle of friends has got to think that I’m a reasonably entertaining person to be around,” she protests. “But I don’t know. I always hate when people go, ‘No, no, I’m really funny! Trust me!’”

In all fairness, The Forgotten Arm is much more than just a mood-crushing story. It’s a masterful, sweet, slow-rocking album that offers redemption in its own weird way. It’s also her most intriguing release since the 1999 soundtrack for “Magnolia,” another fine tale of misery and salvation.

The majority of The Forgotten Arm was recorded live in the span of about a week, which gives it a more open, more summery feel than most of Mann’s recent work. “The themes on this record can be kind of tough themes, and I wanted the sound of the record and the vibe of it to be kind of a bright and fresh and sort of spontaneous feeling, like a more optimistic feeling,” she explains.

One of the main themes concerns that longing everyone gets from time to time to throw everything he owns into the trunk of his car, hit the open highway and start a new life somewhere where the grass is greener. It’s a great American storyline, something for which Mann has a real weakness.

“I really see the pathos in that idea, that people have a life that they’re unhappy with, and they have a desperate hope that by changing their location, that they can change their life somehow. And of course it never works,” she laughs. “I totally know it can’t work. But still, when I think about it, I’m like, ‘Aw, really? Can’t it? C’mon! Mexico, totally different country – surely that would make a difference! Sombreros and margaritas! It’s gotta be paradise!’”

It’s the kind of daydream that sounds very romantic until you’re actually out on that highway, broke and hungry and running on fumes. “Until you have an upset stomach and a flat tire and the two of you are fighting in the front seat about whose turn it is to drive!” Mann giggles.

You’re doomed to fail, but you try anyway, because failing is better than doing nothing at all: there’s the crux of The Forgotten Arm. Not exactly feel-good material. But Mann throws in a surprise at the end by actually giving the story a kind of resolution, if not a happy ending. The sun is poking through the clouds, and you can almost hear Mann squinting in the light.

“I tried to write a happy ending. I don’t think it’s a sad story,” she admits.

“But who’s really cheerful anyway? Who really writes cheerful, happy songs?” she whines, betraying herself with another giggle. “Besides that song ‘Walking on Sunshine’ by Katrina and The Waves. That was my peer group when I was in ’Til Tuesday! I remember she was beating us on the charts!”

These days, the only beatings going on in Mann’s life take place in a regulation boxing ring. The petite songstress recently started sparring as hobby, which sounds cute until she lands a right hook on your face. As it turns out, Mann has a natural gift for boxing, and it’s become her favorite off-stage activity. So go ahead, call her “Ms. Misery” one more time to her face.

“I had met somebody that I became very good friends with, and he was a boxer, and he kind of gave me a casual boxing lesson. And he was very encouraging. He was like, ‘You’re a natural!’ So I had enough encouragement to actually start taking lessons for real,” she explains. “I sort of based some of the character of John on him, because he’s also a drug addict, and he had relapsed, so I was kind of trying to deal with that a little bit.”

The Forgotten Arm (named after a boxing move), like all of Mann’s albums, was released through her own label, SuperEgo Records. Because of that, it will sell only a fraction of what it potentially could on a major label – but the fact that she gets to maintain complete creative control, plus the fact that she makes a ton more money than she would with a major-label deal, makes it a pretty good tradeoff.

“I think if I was on a major label and getting a gigantic promotional push, to me that kind of pressure makes you sort of uncomfortable,” she says. “There are certain artists that to me are almost like athletes. It’s very sporty almost. Like Britney Spears, she’s like a sports figure almost. She gets out there and she dances and she sells it and she does a million tours. She appears everywhere and she’s all dressed up. It’s very sporty. It takes a lot of muscular energy that I just don’t have.”

Even after all of the boxing lessons?

“Well, the boxing is like, all I want to do is fight,” she says guiltily. “I never do all the conditioning stuff that they tell you to do. I don’t do any of the rope work. All I want to do is spar. It’s terrible. I just want to get to the good part!”