Okay, first of all, the hair. Book: Blonde. Stated directly: "... and a pretty girl, her blond hair curled like a princess's." ~Page 56, The Lightning Thief, Rick Riordan
In the movie: Brown. Epic fail.
Second, eyes. Book: Grey. "...except her grey eyes ruined the image." ~Page 63, The Lightning Thief, Rick Riordan
In the movie: Brown. Just, no.
Third, age: In the book, both Annabeth, and Percy are twelve. In the movie, they're like, 19. That is a seven year age difference. Seven years. Why?
Fourth: Relationship: So, in the books, Annabeth liked Luke and was outraged that he would betray them. In the movie, she's just sort of like, "Meh". She doesn't really show much emotion about it. In the books, Annabeth likes Percy, but doesn't tell him. ("You drool in your sleep." "Seaweed Brain.") In the movie, she says, "I have feelings for you, I'm just not sure if they're positive or negative." Or something like that.
Fifth: Personality/Character Development: In the books, you learn a lot about Annabeth's back-story. Her dad, her step-family, how she ran away, etc. In the movies, you know she ran away, but that's about it. In the books, Annabeth is super smart, and she thinks Percy is an idiot (Which, of course, he is.), she's this awesome, nerdy, clever, definitely would be in Ravenclaw, 12 year old daughter of Athena. But in the movies, she's, well, more of an Aphrodite girl (No offence). She's beautiful, and good in battle, and you kind of get the impression that she's a strategist, but not as much as in the books. You don't see the whole thing where she wants to build an awesome monument. You don't see the thing with the sirens. You don't see what happens when Percy gets turned into a guinea pig. You don't see the scene when she wants Percy on her CTF team. If the movie was just a movie, not based off of a book, her character would be really undeveloped.
Over all, the movie portrayal of Annabeth was shallow, and pathetic. There could have been so many more details. It could have been so much better.
Yours in Demigodishness,
Lindsay N.