I didn't want to clutter my text with lots of footnotes - my main aim is to produce something anyone interested could read in 5 minutes standing on a particular spot. However, my sources so far are as follows:
John Franklin "Waterloo: Hanoverian Correspondence"
Gareth Glover "The Waterloo Archive Volume II: German Sources"
Mark Adkin "The Waterloo Companion"
All are superb and thoroughly recommended. Franklin and Glover are collections of letters, translated expertly from the German, and arranged by battalions and brigades of the Allied army. Adkin has maps, pictures, diagrams, explanations and lots more about many different aspects. If you were going to visit the battlefield and wanted to buy one of them it wold have to be Adkin but be warned, it is A4 format and over 400 pages long so it's not really a handbook.