When you've got a poet who wrote over a thousand poems without any real expectation of being widely published, chances are you'll hear some despair and see some rebellious ideas. Dickinson didn't exactly like being told how or what to write, so her poems tend to reflect a rather restless spirit that's unsatisfied with the world and likes to shake things up (by 19th-century standards, of course).
And hey, the lady had reason to feel a bit dissatisfied. You'd likely feel a bit dissatisfied too if the majority of the world was convinced that your reach should extend as far as your kitchen walls—kind of a dream-crusher for a poet like Dickinson. But was she crushed? We think not. Instead she took those naysayers and turned their misled ideas into revolutionary poetry that redefined the boundaries between the inside and outside worlds.
So what we often get in Dickinson's work are quatrains with unusual form (those dashes) and weird syntax placed in the context of despair and loneliness. Her speakers usually try to come to grips with concepts of meaning and identity while occasionally demonstrating a bit of humor and sarcasm. So it's not always doom and gloom and in fact, we usually do see glimmers of hope and the chance for something beyond the gloom.