Why does it bother the speaker that the book is “decrepit”?

Junior is commenting on how poor his tribe and reservation his. The worn out geometry book represents how little his school has.

My school and my tribe are so poor and sad that we have to study from the same dang books our parents studied from. That is absolutely saddest thing in the world....And let me tell you, that old, old, old decrepit geometry book hit my heart with the force of a nuclear bomb.