Like Field's earlier Waterloo: The French Perspective, this book looks at the fighting around Quatre Bras (2 days before Waterloo) from the perspective of the French. Unlike the earlier book, there are far fewer first-person accounts of this battle -- Waterloo's deep shadow? In terms of strategy, though, the French fight against the allied army at Quatre Bras and their simultaneous battle against the Prussians at Ligny were critical, and I now see far better why.
As well as the excerpts from memoirs and personal accounts, the text includes reprints of some of Napoleon's orders and other missives, written by his commanders or by himself. Since many questions revolve on who was ordered to do what when, reading the actual wording (often strikingly vague but undoubtedly patriotic) illustrates what commanders in the field were working with. Still, it's a drier read than the Waterloo book, though many of these excerpts do carry juicy detail.
The maps are helpful, and the photos include present-day images of the land, buildings, and roads the battle was fought on. Also interesting to see how many times (3? 4?) Wellington was nearly caught or hurt this day.