Giving Tree

I just learned the story of the "giving tree" on the tv show So You Think You Can Dance. I had heard the term the giving tree before, but never knew there was a story to it. It's a book by Shel Silverstein, and the gist of it is there's a tree and a young boy plays on swings and climbing its branches, as a young man he takes the tree's branches to build a house and as a man he cuts down the trunk to make a boat. All that is left is a stump, and the then old man sits on the stumps to rest. The last line of the book just sent shivers down my spine: The tree was happy. I need to find that book and read it.