The short review: If you're going to read a biography of Dickinson, this one is probably your best bet.
The dirty details: I sought this out when I was about 250 pages into Cynthia Griffin Wolff's biography of Dickinson. Hers is a beautiful book, and I intend to finish it; but although it gives valuable context to Dickinson's life, I felt a certain lack in the nuts-and-bolts department. I wanted more basic facts.
This book has them, in abundance. Dickinson herself remains elusive, of course. We may not be able to know how she felt about the terrifying stories in the Sabbath School Visiter [sic], but I was thrilled to know this children's magazine existed and had been read by the poet in her childhood. (Her uncle was the editor and gave Emily and her younger sister Lavinia a subscription.) I was able to find copies online and read some of the actual text for myself, but Habegger offers some extremely representative summaries:
March brought "An Infant Missionary's Dying Gift," which told of Frederick Dewey and how he fell into a barrel of boiling water at the age of three and then gave the missionaries all he had, sixty cents, before expiring.
In August the future poet probably read an excruciating true-life narrative, "The Lost Finger," in which twelve-year-old Elizabeth sticks an index finger into a hole in a "revolving card" at a factory and has the flesh torn away up to the first joint, leaving "about an inch of the clean, white, naked bone." "O!" adds the narrator, "the nerves of that very finger of my own, twitch and tremble as I write it."
I know people worry these days about the violence children are exposed to in video games and the news, and I think they're right to be concerned. I just think it's interesting to keep in mind what used to pass for appropriate recreational reading for kids back in the allegedly good old days.
Anyway. Habegger offers up plenty of documentation -- stories such as these, lists of books and authors Dickinson read and admired (if you have a picture of Elizabeth Barrett Browning hanging in your room, it's safe to say you're a fan), and lots of letters and news articles and, of course, poetry.
This book is probably the best guide to learning as much about Dickinson as it's possible to know from the outside. The reader is still left looking wistfully at the firmly closed door of Emily Dickinson's elusive mind and heart and genius. But no biographer can unlock that chamber, and Habegger is wise enough not to try.
The maximum nerditude postscript: Although I found this book incredibly helpful in my research, I still don't know why Habegger dislikes Martha Dickinson Bianchi, Emily's niece, so much. I'm about to start reading Lives Like Loaded Guns: Emily Dickinson and Her Family's Feuds, in the hope of learning more about the copyright battles that went on after Dickinson's death. Dickinson's niece was certainly involved in those, but so was Dickinson's brother's mistress, as well as that mistress's daughter. Dickinson may have led a quiet life, but her family certainly got up to some interesting shenanigans. Watch this space for more dirt on that subject.