Mara, Daughter of the nile book. if you read and understood this book please help.?

I had to read this book for school and completely didn't understand anything. i dont know who's side she's on and how is she a double spy. I just need help. Now i have to write an essay and im completely confused. Can you just please give me like a quick summary on what it's about and what important things happen in this book! thanxs! i promise you i did read it so please don't say why don't you do your own homework. Thanxs!