I would expect Scout to be a girl, based on the TKAM reference. Like the pp said, though, it is her nickname, and I don't think it's a good choice for a given name at all.
When people are asking about our baby name, I'll joke "oh, it was between that and Boo Radley." Just because it's a great book doesn't automatically make all the names in it good.
You'd be absolutely astonished how few people have heard of To Kill a Mockingbird, though.