Britney Spears' debut on The X Factor this fall is hotly anticipated by TV viewers and music fans alike, but Simon Cowell says viewers hoping for a train wreck will be sorely disappointed.

People magazine quotes Simon as saying, "She's not on the show to be Britney Spears on a TV show. She's actually there to prove to the world there's more to her, and she's got the ability to do this job really well. She's taken the role really seriously."

Simon claims he's "fascinated" by Britney, and the fact that she isn't an egomaniacal diva.

"It's quite interesting because when someone has done what she's done as she has with her career, and being such a public person, you kind of think she is going to be very confident, but in real life she's shy," People quotes him as saying. "There's kind of a mystique about her which I think is what kind of attracted me to her in the place."

What about fellow newbie judge Demi Lovato?  Simon says she's a "total brat," but that's a compliment -- he means that she's "completely fearless" and "irreverent."   Explaining why he chose her, Simon adds, "A lot of people who watch our show are 16, 17, 18 and younger, so we had to have someone I thought on the panel that could reflect that younger audience"

Initially, Simon says he "wasn't sure" his plan to hire Britney and Demi was going to work, but now, he says, "because the two girls are on the panel," he says, "I'm kind of seeing and hearing this in a totally different way."