When The Fellowship of the Ring was released last year, Liv Tyler found herself in the midst of a scandal that had nothing to do with her famous parentage or her love life: Tolkien purists were furious that the screen adaptation made ethereal elf princess Arwen stronger and more important than she was in the books.

"I didn't really know that [controversy] was happening at all until I looked at some of the websites," says Tyler, who concedes that, "we were taking risks with Arwen." But as the actress explains, Peter Jackson and Co. — who felt Arwen needed an energy boost — didn't have to go far to find justification for the character's image enhancement. "We went straight to the bible — the book — and really focused on the appendix and the story of Aragorn and Arwen."

With The Two Towers opening Wednesday, Tyler admits she has come to appreciate LOTR's obsessive following. In fact, she credits one particular fan with helping her research her role. "I have this incredible file that one of the designers, Daniel, made for me," she explains. "He was a huge fan since he was a young boy. So he wrote this beautiful, perfect book for me all about the elves and Arwen and all the different races."

Tyler, who just wrapped her supporting role in Jersey Girl with Jennifer Lopez and Ben Affleck, also revels in some of the more commercial manifestations of Middle Earth mayhem. "[In October], I heard from somebody that there was an Arwen Halloween costume," she says, "and I sent my assistant to go find one, but she didn't find one anywhere. I was really bummed out; I wanted to be Arwen for Halloween. That was one of those moments, where I was like, 'Oh my God, I'm a Halloween costume!'"