Oh, my gosh, I just finished this book and it was the greatest piece of literature I have read in my life...I was a little disappointed that I didn't get to see Hogwarts the same way we did in the previous books, but as I read, I found it was better that way n.n

Besides, how the heck would she have pulled that off?

(SPOILER)And as for Snape and Lily's patronus, I think someone confirmed Lily's was a doe in the book...I don't remember :P