Since this is a children's book, the characters are, at this stage, very black and white. The Dursley's have no redeeming features at all, and Harry is very obviously written to garner sympathy. That said, I don't find that offputting. There's enough humour in her descriptions to prevent the characterisation from becoming heavy handed.

Love that she uses the same things to appeal to boys and girls. Best example of this is Harry's room under the stairs. He's used to spiders, which would make the girls pity him because they think spiders are horrible, and pity's a great way to get little girls to like Harry. Whereas the boys will love that he's not scared of the spiders, which makes up for the fact that he's a dinky little wimpy thing. That lack of fear of the horrible hairy things will help boys to respect him.

And before you tell me off for thinking in such glaring steroetypes: that really is how little girls and boys are. I know. I have loads of cousins around the target age of these books when they came out. That's pretty much how they react to things like that.

I like also that Rowling gives something to the adults as well. The Dursleys are such social climbers, proper unpleasant middle class, and that would make a lot of grown ups chuckle a wee bit. Underneath it, though, you can see that Aunt Petunia at least does properly love her son, revolting ball of lard that he is. There's a little shade of grey there for older readers to appreciate.

As for the wizarding types: Dumbledore's very quickly set as an eccentric with his love of sweets, but we're also introduced to his wisdom. McGonagall is clearly defined as the strong, steady, somewhat tartarish teacher, and Hagrid is the loveable scruff. Simple but effective.