This is quite the adventure - steam punk, mystery, and more.  In the past the Morningstarr twins were responsible for the development of most of New York City as well as fantastical inventions.  Then they disappeared, leaving a mystery and a treasure.

Now, about 150 years later, the cipher has still never been solved and there are people who think change needs to happen.  One change is the purchase and eviction of residents from a famous Morningstarr building.  Twins Tess and Theo and their friend Jamie live in the building and hope to solve the cipher in order to save their home.  But the process and results are not what they expected.

I loved the book for the most part.  I felt it got bogged down a little at times - too much filler between clues and the ending - arg.