First of all this history book is a great supplement or even replacement for many highschool text books. Since it covers a tremendous amount of history and events, beyond just the city of Venice, it can be used as a good overview of power struggles and economic development in Europe from medieval days right up to our time.
This book's greatest strength is to provide context for events we're kind of familiar with but didn't really know how they are all connected. We typically see Venice as a place with a great flair for the theatrical, but how did that come to be? We also know Venice as an important sea port, but how did it fit in with all the other famous harbours?
Although I think this particular book does a better job of teaching history than other history books, I do believe it suffers from the same ailment many other such books suffer from. That defect is not keeping the reader informed as to where we are in time. Certainly times and dates are mentioned but the author will easily take a long diversion into a previous era without explaining how things are connected or even where the current discussion is situated.
The overarching feeling reading this book is that as a reader you're constantly wondering: "ok so where are we right now?" A side effect of this back-and-forth jumping is that you can't decide how to look at the time period currently being discussed. If I need to understand how an event in the 18th century relates to something that happened in the 17th century, then you would at a minimum expect sentences that start with: "Unlike in the 18th century, in the 17th century there were ...". Any linking text or dialog is completely missing here, which is the main reason I gave it 4 stars instead of 5.