"Napoleon's Waterloo Campaign - An Alternative History" by Steven Marthinsen
Available at www.xlibris.com
For those interested in alternative history, this is probably one of the best book on Waterloo.
First part is a very good narrative of the Waterloo Campaign from the invasion of Belgium to the climax of the battle, providing in novell-style all the knowledge available 10 years ago.
Then in second part, Grouchy change his mind and allows Gérard to walk hurriedly, not to distant Bois de Paris, but into the flank of progressing prussians brigades, which have to stop to face him.
Attack on Plancenoit is stopped in its track, the Guard battalions are all available to force decision on british centre, Ziethen has to compell to Blücher order and go south to reinforce Pirch... and at the end, Napoleon wins.
The difficulty was to imagine realistic moves and fights which did not occur, and the author did it rather well, by staying as close as possible to reality, and when needed by "reusing" deeds of other battles.
Of course, a good complement is "Napoleonic Options", collective book well known by some of the contributors to this forum.