The Giving Tree feels like coming home. I LOVE this book, and have fond memories of my mom reading it to me as a chid. The book is about a tree who loves a little boy. As the boy ages, she gives all of herself until there is nothing left to give. I used to think the book was very sweet, but as I've gotten older, I understand the sadness that is within the book.
I would use this book to discuss nature preservation in my classroom. Real trees give of themselves until there is nothing left and we ruin our natural resources, just as in the book. This is a good introduction to a "Reduce, Reuse, Recycle" unit.