First of all, don't even attempt this book without reading Wool, and then Shift. I recommend reading them recently.
Dust continues on immediately after Shift, introducing some new supporting characters and giving us the perspective of some that were introduced in Shift. This is still Juliette's story though and it takes us through new challenges that she faces as Mayor.
It's another great read from Hugh Howey, although I think Wool is his best work. Burn answers some necessary questions.
Enjoy.