Emily Dickinson, a creative poet of the 19th century, was known only by a small circle during her lifetime. It wasn't until after her death that most of her poems were published. Her life and work still fascinate readers and are studied widely. Listed here alphabetically by title.
1. The Diary of Emily Dickinson
by Jamie Fuller, Marlene McLoughlin (Illustrator). This fictional diary of Dickinson (wouldn't we love it if she had left a journal!) is a creative approach to biography. It really does come off well. 
2. Emily Dickinson: A Collection of Critical Essays (New Century Views, 12)
by Judith Farr (Editor), Emily Dickinson. If you want to know what scholars today make of Dickinson and her poetry, here's the book for you. Academic tone. Hardcover.
3. Emily Dickinson and the Art of Belief (Library of Religious Biography)
by Roger Lundin. 1998 biography of Dickinson focuses on her relationship to Christianity, and how her religious ambivalence affected her poems and life. Paperback.4. Emily Dickinson (Radcliffe Biography Series)
by Cynthia Griffin Wolff, R. W. B. Lewis. This 1988 reprint is a classic study of Dickinson's life and how it influenced her poetry. Paperback.5. The Life of Emily Dickinson
by Richard Benson Sewall. National Book Award winner. This biography brings the woman, Emily Dickinson, alive. Not easy to do, with such a complex and secretive life. Paperback.6. The World of Emily Dickinson
by Polly Longsworth. A more recent biography, putting Dickinson into the context of her times. Paperback.