Geek Chic: The Zoey Zone by Margie Palatini is a great novel for tweens. It tells the story of a nerdy 10 year old girl who is hoping for a fairy godmother to assist her in her transformation into a teen. The book encourages tweens to be studious, original, environmentally friendly. Palatini uses the Bashleys (two popular girls) to represent peer pressure and the desire to fit in, and portrays Zoey and her outcast friends as role-models for girls.
The book appeals to tweens by using their lingo and cute images. Fonts vary too much for my taste but I believe a tween would enjoy the use of bold, italics and cursive that give emphasis and voice to parts of the 1st person narrative.
Check out http://www.geekchicthezoeyzone.com/ for a sample of the book.
As a geek-girl myself would encourage young readers to read about Zoey and be proud to unleash their inner-geek.