There is a new book coming out about Thoreau, The Trouble With Henry: A Tale of Walden Pond by Deborah O'Neal and Angela Westengard. This is their first book. I have not seen it but it is illustrated by S.D. Schindler whose work I always enjoy.
The book speaks to the importance of the environment and conservation. It encourages individuality and standing up for what you believe in, even in the face of great opposition. The characters in the book are colorful and fun and are used in clever ways to symbolize the Victorian stuffiness and materialistic nature of the people of Concord at the time.
Some of the book's characters are based on real people in Thoreau's life. Some of his descriptions are found in simplistic form for children to understand and Thoreau's own created words are used to describe the sounds of nature found at Walden Pond.
This book and D.B. Johnson's books, Henry Hikes to Fitchburg, Henry Builds a Cabin, Henry Climbs a Mountain, Henry Works, would be a nice change from The Lorax or (shudder) The Berenstain Bears Don't Pollute (Anymore) for Earth Day or environmental units.