Fantastic! Your whole modern Olympians series is well-drawn and pretty clever, but as Athena is as ever my favorite so I had to comment here (though I'll happily comment on the others too, if you like).
Anyway, I love this Athena. First off, her attire is perfect: comfortable-looking with just a bit of understated style (I'm thinking particularly of the shoes here). Feminine, but not girly, if that makes sense. Practical, mostly. The book is an obvious but necessary attribute, but I like how hidden the other two attributes are: you just might just miss the owl on her sweater (and a sweater is a perfect aegis for her -- a unisex outfit that's loose-fitting), and the olive sprig in her hair adds another feminine touch (along with the bangs, softening her otherwise bound-up hair). And I also like that you made her a brunette: there's no reason that she has to be one, but for some reason Athena just strikes me as a brunette. *shrug*
So yeah, uh, short version: I like it!