Robin McKinley's Blue Sword and The Hero and the Crown are two of my favorite YA books. Her new book is Dragonhaven and it is even better than the other two - the best thing she has written and one of the very best things I've read this year.
The story is about a dragon and human bonding - which is its own subgenre in fantasy writing - with large doses of ecology, linguistics, and federal politics. Read this whether you have read the other two or not - this book is not necessarily connected to the others, though I wonder if it perhaps takes place on the same world, 200 years or so after The Hero and the Crown. As soon as this comes out in paperback, I'll be buying multiple copies so I have them onhand to sprinkle on people saying "you have GOT to read this book!".