Siborne's history provides one of the most detailed accounts of Waterloo from the English perspective, and is the must-read book for anyone with a serious interest in the battle and campaign. I emphasize campaign, because the book also describes the often ignored aftermath of Waterloo, when the French tried to hold off the invading Prussian and and Anglo-Allied armies.
This book contains a wealth of information not found in the general Waterloo histories, including an analysis of Napoleon's actions that lead you to believe his campaign was lost on the first day. It also describes in fascinating detail the repulse of the final Old Guard assault, and the ensuing retreat of the French. While most histories lead you to believe that the repulse turned into an instant rout, Siborne instead paints the action after the Guard's defeat as a series of continual Allied attacks and French defensive actions.
Having said that, this is not the book for first-time Waterlooeans. Siborne's writing style is 18th-century florid at its worst. The prose is truly difficult to dig through at times. Also, the wealth of detail may be too much for readers not terribly familar with the battle. Readers not familiar with Waterloo should start with one of the more accessible histories, such as David Howarth's "Waterloo: A Near Run Thing," David Chandler's "Waterloo: The Hundred Days," or the Osprey series book on the battle. Siborne's work then provides an excellent next step for those wishing to delve further into this ever intriguing battle.