Mistmantle Chronicles (books 1-5) by M I Mcallister, also in audio format. It is about a squirrel's quest on and for the Kingdom of Mistmantle. Ultimately, like many other such books, a quest for himself.
Philip Pullman:
His Dark Materials (Nothern Lights/Golden Compass, The Subtle Knife, The Amber Spyglass), also in audio format. This triology is anti Judeo-Christian and can easily corrupt young minds. I would say that it is rather a dangerous set of books for young readers or for that matter, adults readers that do not yet have a committed Christian faith.
The reader will not deny what a great writer Pullman is. I would put him at the same level (in terms of writing skills, the scope of imagination and the clever crafting of theological message) as C. S. Lewis. Only difference is that Lewis speaks for the Godly kingdom while as Pullman speaks for the Satanic beings. Of course, Pullman's definition of Satanic beings are drastly different from that of a Christian believer. It is just the very opposite.
Interestingly, the reading reminds me of two things: the movie of Avator, particularly when Mary Marlone was in the world of Mulefa in Amber Spyglass; and 金庸's books. You will know what I mean when you read the books. Or I could elaborate a bit when I have a little time.