List Maniac 22 - Books About Sisters

I've got a sister (Boo) and I large extended family, most of which is female, so sisterhood is something I get, and I love, and, as a consequence, I love books about sisters, so, for this month's List Maniac I chose to write about awesome books about sisters.
Kat, Incorrigible by Stephanie BurgisWith magic and a dash of Cinderella, this story is all about the relationship between Kat and her two older sisters; and it's funny and sweet. Plus it shows that you don't have to get along all the time to have a great, loving relationship with your sisters. Is in this aspect - magic and all - that Kat, Incorrigible is it's most believable.
The Key To the Golden Firebird by Maureen JohnsonThis is a book about three very different sisters trying to cope with the devastating loss of their beloved father. They had very distinct personalities and they often take each other for granted and disappoint each other; but when it matters the most, Brooks, May and Palmer definitely support one another, and their bond asserts itself, powerful as ever.
The Two Princesses of Bamarre by Gail Carson LevineI believe I have talked about how much I love this book, how this was the story that helped me understand my relationship with my sister just a little better, and it means the world to me because of that. Addie and Meryl are completely different - one cowardly, the other brave - but both of them are willing to do whatever it takes to make sure the other is happy.
All American Girl / Ready or Not by Meg CabotThere are many things I love about these two books, like the fact they were written by Meg Cabot or that it's so, so funny; or the fact that Meg Cabot completely surprised me by going THERE in Ready or Not. But the thing I love the most is Lucy and Sam. Sam vaguely covets Lucy's boyfriend for a while, and Lucy is always trying to steal everybody's thunder; but there is a lot of humor and warmth between them and they have so many "it only happens between sisters" moments!
Girl Overboard by Justina Chen Headley
This isn't, perhaps, the most obvious choice of a book to put on this list, but family is such a major theme through out the story. Grace and Syrah are half sisters, who have never gotten along. Grace is much older and she's convinced Syrah is a spoiled brat who didn't have to suffer like she did while their father was getting rich. And Syrah thinks Grace resents her because Grace's parents split and their dad married her much younger Mom. But, through a set of incidents, they realize that they aren't as different from each other as they thought, and that it's never too late to love and befriend your sister. Plus, there is an extra set of sisters, Lillian and Amanda, who were just awesome. 
So, that's me and my love for sister-books, what about you? do you know of other books about sisters?
Love, Alex.