When I was a kid, this was one of my favorite books. However, I am not sure that I ever actually read it. I think my mom read it to me and my brother and sister. She had this really funny habit of falling asleep while she was reading. Her eyes would be closed, but she would still be saying things, things that usually made very little sense. We always loved it when this happened, and tried not to laugh too loudly, which would cause her to wake up.
In short, the book is about Louis, a trumpeter swan that is born mute. Befriended by a boy named Sam, the swan learns how to read and write, and eventually learns how to play the trumpet to compensate for his inability to make the appropriate swan noises. Louis's trumpet-playing abilities take him to many different places, and make him famous.
White does a great job of mixing in the absurd with the ordinary. The people in the story are initially taken aback by a swan that can read, write, and play a trumpet, but they quickly become okay with it. In one part of the book Sam's dad asks his son if he has heard from his friend Louis recently. Sam replies that Louis has not written him in a while. And the father seems to be alright with the fact that his son has just told him that a bird has not written him in a while.
White's love for animals and nature really comes through in this book, as it does in Charlotte's Web and Stuart Little. I loved this book as a kid, and I thoroughly enjoyed reading it as a budding pseudo-adult.