I picked this book up after hearing it described as The Adventures of Beekle: The Unimaginary Friend meets Neil Gaiman. I have to agree with that assessment; I've been telling parents about it all week as a last minute gift idea for kids around ages 8-10.
Amanda Shufflepup might not have realized she needed a friend until one showed up in the wardrobe. Rudger was just what she wanted, except no one else could see him. The two have great adventures until the day someone else does see Rudger. Mr. Bunting is greatly dangerous to imaginaries. In fact, because of him, Amanda and Rudger are separated, and Rudger finds himself running for his life. Most important of all is his need to find Amanda again before she forgets him; can he survive if there is no one to imagine him?
For anyone who ever had an imaginary friend, this is a treasure. If you were the kid who played along when someone else dreamed up friends, this might make you believe just a little more.