OK — this is the wild card book, but who said poetry can't teach us things? American poet Mary Oliver's selection of poetry and essays, Wild Iris, can teach you through poetic example, I would argue, how to be happy.
Compared to Whitman, Thoreau, and Dickinson, Oliver finds truth in nature and the lessons it can teach. As an observer, we can learn gratitude from the sheer beauty that's around us; or we could imagine being like a "field full of roses," learning that:
Fear has not yet occurred to them, nor ambition.
Reason they have not yet thought of.
Neither do they ask how long they must be roses, and then what.
Or any other foolish question.
— from "Roses, Late Summer"