It would have been better if this book had ended by saying that the boy took the remains of the tree to be harvested and then put into a wood chipper and turned into pulp and then dried out and bonded and rolled and coated and then eventually made into a copy of the book The Giving Tree.
That would make it more of a forehead-slapper.
When reviewing a book for GoodReads or something, I say to myself: "Did I slap my forehead upon completion of this book? No? AUTOMATIC DEDUCTION OF ONE STAR!"