What story does it tell?
How does it tell it?
Does it allow for different levels of interrogation that can be seen or used on the part of the reader? eg can they drill down to discover more detail?
Are you able to create multiple stories from it? If so what are they?
What can you say about the visual design- layout, colour, typography, visualisation style?
What improvements would you suggest?
Where does the data came from, and comment on it’s source.