Hon Otoko, what you did took courage. But "I want to look attractive that way I have a chance of her falling for me", is a wrong frame of mind to go.
One, thinking that if you do something so that she will 'fall for you', is kinda stupid coz it mostly never happens.
And just looking attractive aint going to get you the girl either. I'm sure you have noticed great looking girls with some guy who's either a bit overweight or not very attractive physically, so you can tell from that that girls dont go for 'just attractive'.
This girl of yours agreed to a date with you and gave you her number, in my opinion, is because, as I said, took a lot of courage to do what you did at the bookstore (I mean, you could have gotten beaten up badly by her bf/ex). So I think she is attracted to that courage of yours (and so you are not a coward, you just think you are), so if you wanna get out of the 'geek' shell and become bf material, you dont wanna be a wussy, it wasn't because you are a wussy that the girl agreed to go out on a date with you.
Anyways, I'm similar to what you are, Hon Otoko. I like books too and even though I try not to look it (with bleached hair and stuff), I am technically a geek too. And hey, I thought, like you did, that if I bleached my hair it would shake off my geekiness and make me more attractive in girls' eyes. Guess what? It doesn't work, though I still bleach my hair coz I like it now. Even though I'm still alone (though I was in a relationship in just under 2 months), I now can at least have girls talking to me as I try to talk to them. It doesn't land me a gf, but it's a start.
Anyways, all I can end this with is the cliche "be yourself". If you did read/watch Densha Otoko you will remember at the end that he was being himself, as an otaku.