My Uncle Emily by Jane Yolen, illustrated by Nancy Carpenter

From chapters.ca:
This six- year- old has an uncle like no other His uncle wears long white dresses and never smokes cigars. Gilbert s uncle is none other than Emily Dickinson... Uncle Emily he calls her. And how he loves her. He knows that she writes poems about everything, even dead bees. But it's a poem about truth that, after a fracas in school, he remembers best. Tell all the Truth, the poem begins. And, in finally admitting what went on that day, he learns something firsthand about her poetry, something about her, and a good deal about the importance of telling the truth, no matter how difficult it might be.