Andrew Roberts' fast-paced, exhilarating account of the battle is one of the most readable around. Highly recommended as an introduction.
David Howarth was a British war correspondent who produced this masterful account in the 1960s. It's now considered a classic, and was the book that first got me hooked on the battle.
Extraordinary Editions specialise in beautifully produced collections of eyewitness testimony and artwork. Their Waterloo anthology is a limited-edition collector's piece, and a beautiful thing for any military history enthusiast to own.
Waterloo 1815 - A Commemorative Anthology
By Extraordinary Editions