There are 23 scenarios, including one for the entire Wagram battle, and then three smaller scenarios that break the battle into smaller pieces. The size of the scenarios varies from a few divisions to Wagram.
I don't play Field of Battle, but it will be quite simple to convert the OB's to Volley and Bayonet.
One of the features I like about the scenario format is that each comes with two maps; one with only the terrain, and a second with the troop deployment. Nice touch.
I haven't decided which of the scenarios I will play first, but I will be painting more Austrians. I also recommend the Blunders on the Danube blog. It is a great resource.